There are guys doing big SxS trips in fact I've been chatting with some guys doing Mexico to Alaska over a few week period. Obviously you have to be a little more careful with your packing, payload and weights but if guys can drive around the world on a motorbike certainly it could be done on a SxS outside of legal challenges.
I would love to see how everyone has a sxs setup for long trips. I need to do something about extra fuel. With all the rzr's burning up I'm worried about where to put extra gas