Once I could afford a backup, I got a backup and used to carry it. 10 years ago I stopped because it had been a very long time since I had a problem on a gig. In the last few months I've had a couple close calls but I fixed them before the gig. Have considered bringing a backup again because of it. Still very undecided, though, because I hate switching basses during a gig and I hate dealing with everything involved in having two basses onstage...the extra stand, the extra weight of a double gig bag on my back, bringing an upright and more than one electric bass, too...
But despite taking the time to type this, I don't really care what any of you think of my professionalism since I do it for a living
So fate is sending you messages and you choose to ignore them? Not a good plan!
Of course "backup" depends on the situation. You know I HATE changing strings in the middle of a gig. I hate everything involved with it. I hate carrying them along, I hate pulling the old pieces out of the bridge and tuners, I hate feeding the new one in through the holes! That's why I took all the spare strings out of my bass cases! NOT!
Sure changing strings in the middle of a gig IS a pain. But still better than playing on three strings. And it's not just playing rough as some have suggested. I've had a new set of strings that were just plain brittle. I recently had TWO strings snap at the same time (were NEW GHS pressure-wounds). (luckily was before a gig and not during)
I agree that two basses on stage are a bigger pain. That's why I only do that when I WANT two basses there to play (eg. fretted and fretless etc.)
But "backup" to me says "What do I do If "this" happens?" For me that's things like change a string if it breaks (from other set in case, each bass has a spare set of strings used on THAT bass), Grab spare cable from case (each case has spare cheapo cord in there), make necessary adjustments or install new battery, (each case has set of allen wrenches and cheap multi-tools to do ALL screws etc. on THAT bass). And it includes trying to have basses that do passive-active switching (not all are like this). Also included in "backup" are basses, straps, cords etc. you can borrow from other bands, guitar player, the venue etc. just depends on each situation.
But of course the ultimate is a whole 'nother bass. Personally I don't worry about having a backup on stage. For me, a junk bar-bass in the truck is close enough. And let me say that I HAVE had to drive home for another bass and is it NOT professional, and really makes the band look bad. A trip to the truck, however, is just a rescheduling of a break or some other cover. Same goes for the DI carried for amp failures. Sure using the PA for bass is often less than optimum, but certainly more optimum than no bass at all! I've had to use that DI a couple times too!
Point is once the crap is in my bass cases, I don't need to think about it again unless disaster strikes. Same for bar-bass in truck. Having had my nose rubbed in "what if" a few times, I'm not about to see how far I can press my luck. Maybe Bowser doesn't care if his bass player takes off to deal with some problem, but while most people understand that things can go wrong, I've found they are much more understanding if you immediately deal with the problem and get the show back on the road.
Say wait a minute! You are bringing an upright and an electric? Well then you ARE bringing a backup bass! So why would you need two electrics unless you really want that for the tone difference?