Q: Apple TV drops WFI and will not connect

I have two apple TVs.  I set them up and they connect to WIFI fine.  I come back some time later (days,weeks,month,etc.) and I cannot connect to internet.  I turn off wireless router for several minutes, restart Apple TV, and I still can not connect.  I do not have the option to connect to ethernet.  Is there something I can do to fix the problem and prevent it from happening over and over.