One thing would be to remove the delete connection data as described on the image download page.
If the wifi strength is not good enough such disconnections may happen. You should configure your dhcp server (in router normally) to always assign same ip to the pi3 mac address. That way you at least keep same ip. If strength is too bad you should consider using ethernet instead.
Next release will get some imrovements in wifi handling, but it can not change how good connection is of course. This depends on wifi module, position in room, shielding ...
