I definitely have the same problem. I started commuting on a GT Timberline (which although new was definitely a beater). I got a Kona Jake to be my "nice bike" and suddenly discovered that I couldn't stand the sight of the Timberline anymore. So I bought a Marin Muirwoods to be my "bad weather" bike. I just finished upgrading the Marin to a full XT drive train, and I'm in the process of stepping the Jake up to Ultegra components.

Trouble is, now I've got a drawer full of enough components to make two more bikes, and I can't help thinking these frames aren't worthy of the components I've got on them. So, if I bought a Major Jake frameset, I could move the Ultegra components there and put the Tiagra group back on the Jake. But then I probably wouldn't be satisfied with those components.... And so on.