Oil won't have anything to do with clutch wear....andIf you're getting 5000 miles out of a sled clutch, I'd say you're just easy on stuff and that's why you've had good "luck." I would guess it's simply that you arent an animal, and take care of your stuff.
The thing with sleds is, most of the guys who complain the most and have bad "luck," are guys who also store their sleds under a tree with no cover, no maintenance, and hit stuff every time out. And are then immediately concerned about warranty...which they don't really understand how a warranty works. So it shows a disproportionate amount of failures on things like forums. Not that there's no exceptions to that....but there is a LOT of that in the sled world.