Very broad question here. I don't know exactly what the problem is but I'll edit this post as we narrow down the possibilities.
I think I'm running into memory constraints.
I'm running a sketch that records two temperature values every 60 seconds and transmits them to an AWS RDB via wifi. It works well for about two hours then stops. I don't know if it's a memory constraint but I suspect that it is. What other common problems (often overlooked by newbies) can cause a sketch to end after a couple hours of run-time?
Is there a simple way to add an instruction to a loop to clear the SRAM?
Arduino UNO + WiFi 101
Edit #1 12/24/2015:
It's the WiFi board. It happily remains connected to my phone's hotspot but only lasts an hour or two on my home network. Working on root cause...any ideas are welcome!
Edit #2 12/25/2015:
Tried to Wifi.disconnect() and reconnect with no luck. Why do some networks kick the board off while others work just fine? Will look into the watchdog.