Its easy to get sucked into building fixies all the time. I had a bunch of them for a while but finally decided I was going overboard. Scaled my bikes back to "a bike for different occasions." 1 track bike, 1 fixed gear cyclocross, 1 road bike commuter, 1 BMX destroyer, 1 bar bike.
The thing about building fixed gear bikes is you end up with a bunch of spare parts laying around, and eventually you look at all the parts and go, "Hey, I could build another one with these parts".