I bought a couple of Aeotec Range Extender 7's and put them in about the middle of the 2 wings of my layout. However, even after a few months it seems very few devices are going through them.
I did do a Z-Wave repair yesterday, hoping the hub would see them as strong signals and route through them, but that didn't seem to be the case.
So:
I have exactly the same experience so you are definitely not alone. ZWave routing is one of the great mysteries of life. One thing I have read is on the C7 a full ZWave repair is not recommended though in some cases an individual device repair may help. But I have repaired a zwave device, had it discover a nearby repeater, only to come back the next day and discover the device is ignoring the repeater again. I do know from asking questions that there is no sort of least-cost routing going on, so the hub will not necessarily pick the "best" route as long as it has "a" route.
Which all begs the question... is your ZWave mesh working ok? If so, maybe just leave well enough alone.
Not scientific, but my rule of thumb is to place them about 2/3 of the distance from the device to the hub as devices seem to ignore the closest option in favor of something closer to the hub.
Doe the device ignore things that are close by in favor of repeaters closer to the hub, or is it the hub that ignores repeaters close to the device in favor of things closer to it?
That is has happened to me also. Out of a total of 43 Z-Wave devices, I have 5 Aeotec Range Extender 7 and 2 Ring Range Extender G2 scattered all over the house and the house is not that large (2,300 sf). Maybe I got a little carried away with the range extenders 
As of today 34 are paired directly to the hub and all the other devices are using other powered switches for repeaters. Not a one is using the Aeotec or Ring.. But the mesh is working OK, so I am not going to complain,
Good question and have some theories on the answer, but just happy that my mesh is working better than ever...
This is my favorite example... I have a Leviton ZWave outlet controlling my office air conditioner. It has a crappy connection and changes routes constantly. Device 06 is a mains-powered repeating device that sits close to the hub.
And in the same room, maybe 6 feet away, I have a repeater... that the Leviton outlet won't use! I've repaired, I've even excluded and re-included. Usually after I do one or the other it starts using the repeater for a while and then reverts to a repeater right next to the hub.
I'm having the same experience as others. Routing is weird. Some devices are connecting directly while another one nearby may be taking a strange route that certainly isn't the shortest path, and may even be taking multiple, unnecessary, jumps. Some are going through one of my Aeotecs, but none are using the other one.
I know Z-Wave Plus is supposed to be "self-healing" but it certainly doesn't seem to be optimizing.
That brings up some other questions: When does the Hub do this self-healing and what happens if you try to use a device that invokes a rule while that is going on? (both if the device is involved in the self-healing at the moment or not). I'm asking because it seems that a lot of the big delays, or even failures I get seems to happen late-ish at night (starting around maybe 10:30-11 pm). I'm wondering if the Hub is in the middle of its internal Z-Wave repair at that moment and the delay is caused by this repair process needing to finish or even losing the request. Is there any way to control when the Z-Wave repair is run? If not, i sure wish there was a way. It seems to me to be analogous to scheduling a computer backup that one wants to run say at 2-3 am not 11 pm.
Unless you manually invoke it, my understanding is that it only happens at route failure (which I believe includes the need to retransmit due to a timeout).
Not sure that it's intended to be optimized in the same sense you (or I) imagine. It's uses Source Routing, which is the opposite to what most people learn/experience. Also, one of the primary goals of the mesh is to route around obstacles. We also can detect its desire to use 'adequate' repeaters over 'strong'. I've always attributed that to a goal of creating the largest sphere. That makes edge-of-sphere repeaters more attractive.
I am seeing the same "weird" routings in my Z-wave system and forgive me for this Heretical thought but i tend to beleive that if something is performing in a way I can not understand and no one can explain, it might, just might be performing bad due to a failiure of design or deployment.
Do not know who's to be blaimed but Z-wave for me (with my 40+ Z-wave devices and 4 repeaters) is not at all a success.
Here is my 2 cents to the equation.
More than two months ago I had a BIG problem with ZWave mesh.
One think I did - installed an Aeotec 7 Repeater plus few more plug in
repeating switches/dimmers just to be a repeaters.
More than two month already passed but neither one is actually became a repeater.
I tried different places specifically for the dedicated Aeotec 7 toy.
It is still doing absolutely nothing.
I had a couple of Rings that sat for about that same time frame before they suddenly became "useful". Had pretty much given up on them until I glanced through the mesh details and saw that they were finally active. Still see some times where their usage is low, but the hub seems to route through them more actively now.
Well, I guess the "real" solution is when we start seeing a lot more 700 series devices and we can pay all over again to replace what we have. (Like paying to get your favorite songs on vinyl, then cassette, then CD and finally downloaded. :-))
One thing I love about the Inovelli's is the extra button that can be used to configure it, but for me, I use it as a "favorite" button and set it to power on lights at a very low setting. So in the morning or late at night I don't have to address Google or Lady A or remember special taps, I just press that little button and get a nice dim light. I know Zooz has 700 series light switches, but they don't have that "favorite" button. My one big dig against the Inovelli switches are that they are so big I had to hire an electrician to get them into a 2 gang box. (I may have an unusual situation as I live in a condo and they have metal boxes in the wall and metal rods attached to the top and bottom so the boxes can't be replaced).
With Inovelli coming out with Zigbee switches I don't know if/when they will be coming out with a 700 version. (Though some of their products are 700 series already). But, hopefully, they will.
FWIW I have an Aeotec repeater on the other side of a wall from my hub and it’s the most used repeater. I have read other doing something similar and having the same results. If you don’t have one close to the hub I would recommend trying. Routing is a crazy mystery.
I have an Aeotec siren about 3 feet from the hub and it, too, is my most used repeater.
Thanks. Maybe I need to move one of them.
I have deployed 4 Ring extenders with zwave gen 7 and 4 Aeon repeaters gen 5.
All AEONs report RSSI 0, all with 25-45 neighbours, despite being line of sight o the HE 12ft away, which was supposed to have operated as a relay for the zwave devices sitting behind big metal freezers working at 9.6kbps and relaying all over the house
After a couple of months NONE of the 62 zwave devices are routing through the repeaters.
Bizarrely several zwave devices are routing through devices the other end of the house and running at 9.6kbps rather than use the repeater 12 inches away.
The whole zwave routing is weird.
I have a zwave device sat one end of the house that routes through a zwave socket the other side of the house behind a fridge - passing through the HE which is midway between them, then back to a third device again passing the HE then finally back to the HE.
Now if zwave is supposed to run wireless networks by routing traffic through an invisible spiders web then it is doing a great job 
I did notice that one AEO repeater is successfully routing via another AEON repeater but apart from that not seeing any benefit at all to adding 8 supported zwave Repeaters after two months of usage, so either they are not really compatible, zwave repair/heal is not working or there is another step required in getting the repeaters working properly.
Honestly that's as good an explanation as I've seen.
I have two Ring repeaters. One was routing for literally everything. The other was doing nothing and had a RSSI of 0 after a couple months. I moved that non-routing repeater 6 foot away to the adjacent bedroom wall outlet, and suddenly the RSSI is 12, and it is routing for about half of my devices.
Funny how turning the repeater 90 degrees, and moving the repeater a short distance away made all the difference in the world.
Download the Hubitat app
