Remote security cam viewing drops-reset router to resume

My brother and I use Swann cam systems with identical Cisco Valet Router.  We tried several routers & Valet seems to work best.  We both have capability of Smart phone viewing and of course Internet viewing.  I don't have much of a problem with cam dropping on internet & phone (although occasionally mine drops too) but my brother's  will drop a couple of times in a day or nights.  Sometimes it may work for a week, no problem , then it starts again.  I'm thinking for some reason when the internet drops, the DVR has trouble reconnecting with the router & the router has to be rebooted and usually it works ok for a day or so.   Any idea out there what might be causing this problem or suggestions.  Thanks.