Almost a year later, but I finally got around to playing with this. I put a Iris V2 ZigBee outlet/switch and a lamp on the end of 200' of extension cord and started walking. It lost connection about 60' feet from the house. Disappointing.
On a whim, I replace the Iris V2 with a Sylvania outlet and did the same thing. It responded immediately all the way to the well head (~175' from the house). I proceeded to wire it into my relay system that controls the well pump, placed the sealed container in the top of the well casing and tested again. Nothing. Turns out, I had pushed the sealed container that contains the relay and switch below ground level and blocked the signal. Once it was back above ground, it worked fine...……..and inside the PVC well casing.
So I thought I would push my luck and try to use the newly installed switch as a repeater for the next 275' jump to my barn. Worked like a champ.
I live in a very rural area with no interference whatsoever, so that's probably why I can push (or exceed) the limits of ZigBee. 275' for now, and I may just see how far beyond that it will go. The whole picture may change when the leaves come out this spring. It's a straight line of sight shot, but one never knows!
Bottom line: Try outlets as repeaters before you spend a lot on long range stuff that you might not need.