I have never brought a backup bass to a gig before. Of course, that doesn't mean it isn't a good idea to bring a backup. I have to say though - a lot of the gigs I've played where a backup would have been an especially good idea (gigs that were a long distance away in remote areas) didn't allow for a backup. By this I mean there simply wasn't enough room in the cramped car for me to bring anything more than one bass.
