Airport Time Capsule losing internet connection after 3 hours

I just got a Time Capsule and my internet connection seems to time out after 3 hours or so. My macbook/iphones/ipad seem to still connect to the internet but there is no internet connection. The only fix seems to be unplugging the modem every 3 hours. I think I have the most updated systems on everything. Does anyone know what I need to do?