Its really hard for me to believe anyone even needs to have a discussion on this. Not that I care what anyone wants to do, but here's a story that happened to me this friday.
I'm playing 3 sets, 60 miles from my house. I'm playing my 1978 Fender Jazz bass, that I have had for a couple months. About halfway through the first set I am thinking "my god, I have the best sounding bass in the whole world" (it was a good tone night) During the next to last song of the 1st set, I can't hear my bass anymore. I stick my head right up next to the cabinet, and I can hear a little noise, but not much. We are in the middle of a song, so I assume my amp crapped out on me, and I plug into my DI box (for emergencies) and I get through the last 2 songs, unable to hear myself. I figure I'm going to have to use the backup head I keep around (for emergencies) (crate powerblock, its tiny as can be, and I figure its insurance for me and my guitar player)
So between the 1st and second sets, I plugged my other bass, which I tune half a step down, into my amp, and its working fine. I then take the control plate off, with the tools that we have around (for emergencies) Everything looks cool, I have no idea whats going on, and I'm kind of freaked out about what happened to my bass, but I just end up retuning my other bass and finishing the night.
Apparently there was something wrong with the tone pot, I cleaned it up, and sprayed contact cleaner in it yesterday, and now its working fine.
Visually it was fine, I don't abuse my gear, and I've been playing it every weekend since I got it a couple months ago.
I think I'm going to buy a small bottle of contact cleaner and throw in my gig bag (for future emergencies)
Now extra strings certainly were not going to save me from the disaster, and I was not going to start poking around this particular bass in the middle of the night with a soldering iron. There was no other band to borrow gear from, and no music store open. Even if was willing to go to walmart and play a first act the rest of the night, that would take way too long.
I am not going to say everyone who doesn't bring a backup bass is unprofessional, but if what happened to me happened to you, what is your plan to take care of it?