I've got 6 basses, and i'm a variant-obsessed owner/player, so all of them are different types: 1 suped-up active/passive modern style Jazz bass, 1 passive beater P-bass that's worth only as much as the pickup i put in it, 1 Musicman Sterling H (with upgraded alnico pup, for more of the standard Ray tone), 1 active dual coil soapbar style bass, 1 fretless Jazz bass, and 1 totally unique insane sounding bass that no one else has (Modulus Quantum 4 turbo w/upgraded 2tek bridge, John east preamp and nordstrand big splits). The thing about having all your basses be different kinds and having them almost all active, is that most of them don't work very well as a backup for any of the others. On the other side of the coin, i feel like i have exactly what i need no matter what situation comes along. I just keep my basses well maintained, and clean/inspect them after each use to make sure nothing might fail on me during the next show, make sure i have backup batteries ready to go, etc.
Depending on the project i am in, I'll dedicate a specific bass to the sound of the band (if it's an original project). Essentially I'll find which of my basses I think sounds best with the musicians I'm working with and choose that to build my tone around. My last band was a heavy, loud rock band and while I had totally used my active jazz for a couple of our shows and it totally kicked ass, and while I'm sure I could have used another bass just as easily, there was something I couldn't stop loving about my specialized Quantum Turbo with the heaviness of that band. It was a harder bass to work with EQ-wise but it sounded so good once I got it dialed in and it gave our band more of it's own sound, so that's all I really used after a point. Essentially, I do the same thing for recording sessions. All my basses are high end and sound great in mixes.
But if I'm in only one project, or only using one bass, mainly, i feel sorta bad neglecting my other basses, so i play them all equally at home. And i try to find projects to use them in.