I remember when I was a "kid", I snapped a string mid-gig. To this day I'm a bit petrified that I'll break a string and not know how to respond. With that said, I've been changing my strings every 4-6 months, not knowing what the life of them actually isAfter reading these posts, I'd say I've been spending too much money on strings...
This happened to me too, just once, back in 1975. I had no spare strings and got through the gig on just 3.
I now carry a spare bass to every gig just in case. I have never had a string break at a gig since. If you have a spare bass then maybe take it to the gig if you have the space. Over the years it will pay for itself on not buying all those new strings!
After reading these posts, I'd say I've been spending too much money on strings...