Once, in 1985, I got rid of my Alembic (Cocobolo, long scale) for a Steinberger, due to the weight and onset of a persistent sore back. It was the biggest mistake I've ever made with an electric musical instrument. Some years later, I was able to talk my brother into selling it back to me (it mostly sat in the case, as it had been killing his back too). Now I concentrate on maintaining good posture (or at least try to) and have introduced a stool or chair into my blues and jazz gig setup. I've also adjusted the strap out a bit, which seems to slightly help. I still play other basses a fair amount, but nothing gives me the musical joy that the Alembic brings. When the sound and my performance really matter, it is worth the extra weight.
John