I’ve had some issues with cores in the field going offline and never coming back.
It’s a core fix, but it’s a strategy I’ll continue to use with P1/photons – reset the Wifi module by cycling WiFi.Off/On if your device is disconnected from WiFi for more than X minutes.
I posted some sample code here [Core] Getting stuck in flashing green (disconnected) bug and fix
It’s hard to predict what bugs exist or will come up in the future, so it’s good to check return values for critical functions (like connectivity) and reset your device if you get too many errors.