I believe in backup guitars. Because I care about my audience, and I care about my band. I don't want anybody to have to "stand by" while I deal with something that I could have prevented by simply grabbing my backup guitar that's sitting tuned up on the stand right behind me. And gear has an awful way of failing just about the time the band is cookin' and has never sounded better!
I for one am not in the "troubleshooting" mode when I get up in front of people to perform music!