Wow, I called applecarea bout the same problem a couple of day ago! How funny.
Well, i also live in a one bedroom apartment, and i normally detect 5-8 networks around my area. Distance should also not be a problem for me, since the computer is only 8 feet away from the Airport Extreme base station. Now, why was it that i kept getting intermittently disconnected from my network??
I found out that all the signals being transmitted by other routers in my building could be a great source for intereference (not washers and dryers, and other electronic equipment near my computer and router, as i had previously thought).
To solve the problem all ihad to do was to strengthen my signal and shorten it's range (stregnthening of the signal sghould be enough, though).
To do that you have to acces the Airport Admin Utility, under Utilities, in Applications. Then select your base station and click on the Configure button. Under the AirPort tab click on Wireles Options... Then check the box next to Enable interference robustness, heighten your Multicast rate (to strengthen your signal), and tweak the slider under Transmitter Power if you desire.
This procedure worked like a charm for me, and will likely work for you!