Ok, so I'm hoping this is an easy fix.

I had my driver's side brake light go out (should have been an easy fix right? Lol). So, I got the manufacturer recommended bulbs and decided to replace both brake lights while I was at it. About two days later a friend pulls up beside me on the road to tell me my passenger side brake light was out. I asked about the driver's side and he said it was working fine.
So, earlier today (3 days after I found out the passenger side brake light was out) I'm told that BOTH sides are now not working. These bulbs were bought and put in less than two weeks ago. All other lights back there (turn signals, parking lights, even the top brake light) are working perfectly fine. Any idea what could be going on here?

 

Did you notice any moisture in the housing when you replaced them the first time? If you have a leak back there it will continue to short out your bulbs. Unless you have stock in Sylvania, grab some of that new spray on rubber. You can find it at most home repair stores, if there is no sign of water leaking, start looking for open or exposed wiring. You might have to remove the crinkle casing from around the wiring to see if there is any moisture or exposure. Just make sure you rewrap everything in electrical tape when done!