In high school and college, I switched between bass and guitar, but never within a single band. Then, in a cover band in law school I switched between bass, guitar, lead vocals, and being entirely off stage. It depended largely on who had showed up at practice when we learned the song, but also on vocal range, whether our primary lead guitarist was willing to learn the song on guitar, and other stuff I don't remember. It was loads of fun. I haven't played guitar on stage since that band's final gig in 1992, some of which strangely ended up on Japanese TV, but that's another story!
At home, I spend at least as much time on guitar as bass, unless I need to learn lots of material on bass for a band or project. I recently joined a cover band, so I've been learning loads of tracks, and have barely touched my guitars for the past couple of months.