As others have said, if you're gigging, two basses are a must. There's just no way I would go to a gig with one bass, as you just never know what may happen. I can totally get how a bedroom bassist may have one holy grail bass and not care about any others though. A decade or so ago I was in that position, when really the only other basses hanging around were just waiting to be sold after being "replaced". For financial reasons, a combination of expensive taste and lack of disposable income, I now actually only ever have two basses at any time.
Conversely, I use a Quad Cortex now for all effects/DI needs, and my only backup for that is plugging into the house amp/DI. I effectively take all of my equipment to every gig as a result!