Hard wire if it's possible,
windows contacts most better wireless in my view for aesthetics and headache
Some service every 6-12 months, some after a few years, some people wait until a fault develops, that's advantage of contract , they do the service and book it in as matter of course
Good solid wireless system doesn't have many call outs ,except if your WiFi isn't behaving , then you might opt for dual path and gsm option addition
If your not competent get your installer to move devices, most usually mess it up trying to avoid paying, it's normal