Connection Drops

I'm having the same issue on my 2012 rMBP. It's extremely frustrating and I can't find a fix. This is the first time I've seen someone else with the problem, maybe someone will come around with a past experience and fix.

 

Which WiFi routers are you using?

 

Are both on 10.8.2, this might be the problem, and you just have to wait until Apple fixes this.

It also might be the router, a reset can solve problems, or choosing a different channel on the router.
These things are extremely hard for "us" to solve if you don't know where the problem lies, most of the time though an Apple router will work better, if you have such a device then the only thing you can do is to wait for Apple to fix this, and they are not the best regarding wifi.

 

I actually just had a Genius Bar appointment today about this issue with our 2011 iMac. The problem was exclusive to that machine, since all other devices in the house stayed connected just fine. As you said, turning Wi-Fi on and back off was the way to temporarily fix it, but the issue would always come back.

The Genius's solution was to go in to the Network pane of System Preferences. At the top, there is a drop-down labelled "Location". If it is set to "Automatic", select "Edit Locations" and create a new one, then connect to your network as you normally would. Apparently the "Automatic" setting can bug out after a while and randomly drop the connection. We just did this this afternoon, but already we're free of the Wi-Fi drops that used to occur every 20 minutes or so.

I can't say for certain that this works 100% of the time, but it seems to have fixed my issue so far, and it's a pretty easy thing to do. I'd say give it a shot!