I have ~130 devices connected to my Raspbee II, latest firmware, latest deconz (non-beta).
Now, every now and then, a device lose connection and needs to be re-paired. I had an unlucky last week when I had to repair 4 devices. Usually it’s not that bad (once per month). This so far happened with different devices, it doesn’t seem to be brand/model specific (a thermostat, 2 different philips bulbs model, a ledvance bulb).
I guess that when the number of devices grow, it might be natural that every now and then one does something weird, and so needs to be repaired, but I was wondering what would could it be doing to just reset itself? I guess the answer can be “anything!” but wondering if anyone has a clue 
Having said this, this is not at all a huge problem in my setup, I can repair a bulb device every now and then.
will try to get some next time it happens