Know it is not exactly the point of this thread, but I like to stick to one bass in all aspects of playing, that is ideally giving 1 single main bass as much attention as possible regardless of weather it is in the context of home practicing, band rehearsal or gigging.
Actually the only time I don't really mind using different instruments and will do so without second thoughts is when recording, since it is much more important to get the exact right instrument for the job in that context.
More on topic I was once part of a band where we would all take turns in playing the different instruments of the respective songs as well as taking turns in handling the vocal duties, I for instance both played electric guitar and bass, heck even drums on a couple of songs that only required a relatively simple drum beat, as well as I was shifting between doing lead, backing and no vocals too, I guess born from the fact that we would all more or less equally contribute with songs to the project, and the fact that the core concept was sort of an "all stars" singer/songwriter band, all members being part of different other actively gigging and well known original main musical projects and bands on the local music scene at that time.
Mind it was a rather short lived band, but we did get to play one live gig, and contrary to what one might have thought the transitions between instruments actually went pretty seamlessly and naturally, not really interfering with the overall flow of our show or appearing odd, I guess maybe because it was how we rehearsed the different songs too, so that we were used to swapping around fairly quickly without much fuzz, as well as I guess that since it was done so consequently it kind of worked out as an integrated part of the concept of the band and our show, sort of becoming a curious feature, rather than an interfering inconvenience.
