Gross - with over 200 devices and most of those zwave - I already get latency on some routines (like door/motion activation of a light). For that reason I have avoided the 5s poller routines.
But I have had devices stop responding (sometimes unreported low batteries, sometimes wall switches or plugs that just won't communicate). To that end, I am running Device Watchdog once a day to report on any device that hasn't checked in for 24 hours.
Unfortunately, a lot of plugs and switches (zwave mostly not zw+) will go days on end without any communication. So my solution is to run a refresh 2x daily to all devices that accept the command.
Then today I noticed 2 of my 17 Keen vents had not reported and when I ran a manual refresh from the device - they reported back (so not dead batteries). Then I questioned why my "Poller" routine hadn't pinged them and found they aren't in the list of devices. @napalmcsr lead me in the right direction to use a custom action - which seems to do the job.
Now my "other" thread Need Rule - Refresh if Last Activity > x time would really help me reduce my unnecessary network noise - if someone could help me build the RM I need 
