When I was gigging regularly, I made sure I had backups nearby for both my stage guitars- a 12str and a 6. However, I also seemed to have a pretty decent run of good luck and almost never needed the backups, only pulling them out once every few months to "give them some air", as it were. In fact, my luck was that I only broke one string on the 12 in performance in over a decade, so I consider that as doin' pretty good.
But that also meant the duplicates (and they were- as close as possible to the #1's, and thus set me back a decent chunk of income) quickly became essentially case queens, mostly ignored, seldom used, although I did try and change the strings etc somewhat regularly. When I stopped the constant gigging, they went into the closet and stayed there for a couple of years until I finally sold them off- simply didn't need them any more.
Backups are good, but after my experience, I don't think I would spend that much on a couple of potential closet keepers again. Basic, simple and to the point would've been less expensive.
