I think older devices have a greater need to be closer to the Vera when pairing. The oldest devices in my network are now around the five year mark, and many of them will not pair unless the Vera is within a meter or two. There are even a couple of oddballs that won't pair unless the Vera is literally right on top of them. And for some devices, the inclusion will appear to succeed at some distance, but then fail moments later in device configuration. Moving them closer together and trying again usually resolves that. Newer devices seem to fare a bit better, and distance-related behaviors overall with the Vera Plus vs Vera 3 are noticeably improved.
I've used @fbrown's approach, but I find that devices are not as stable initially vs if I take the time to do them in place. My guess is that part of the initialization process for many devices at pairing is neighbor discovery (both new device and its new neighbors), an important step in building the mesh properly, so now, I include devices as close to in-situ as possible. This has reliably improved my inclusions.
The downside of this, however, is that I have on occasion bricked my Vera (Plus) during inclusion. I usually wait a minute or two before unplugging it and moving it to the next device or back to its usual home, just to be sure it's finished its tasks and gone quiet. Alas, that seems to not be enough. Every once in a while, I get disappointed, and when plugging the Vera back in, I'll get to a blinking or solid power light and no further. I've learned how to resolve this for myself, and it's troubling to me, because the nature of the crash is a corruption to which the underlying system should be immune, but apparently, it is not (it's an OpenWRT thing, not directly Vera's problem). So key to the practice is this advice:
However you do it, take your time, let things settle as you go, and try to avoid doing too many things at once. And absolutely, positively back up (with Z-wave network backup update) your Vera before doing any inclusions or exclusions. If things go badly, you'll be glad you did. Time well spent.
