Cat clutches are throw aways. Run them until they're worn out, junk (pre-'16). '16+ Cat's are great sleds overall and have Team clutches. I know people say these motors are bullet proof, but they still need pistons. Towed out a '16 last year after it dropped a skirt and locked up tight, just over 4k miles, no warning just a bang. Ridden hard. Took out case, cylinder, head, and pistons. Crank was salvageable. Same thing happened a different weekend with an '08, but I don't know mileage on that sled or what kind of service it saw.
My '13 XM has around 8k miles or so (exact miles unknown due to gauge failure & replacement, but 502 hours on ECU). It's lived a hard life, but I do maintain it, and it's never been towed out. Center punched a tree early on; replaced pipe, plastics, and eventually S-mod. At about 3800 miles I replaced OEM pistons; the skirts measured beyond the limit for collapse. At ~5500 miles I put a crank in it, one connecting rod was discolored from heat and the other wasn't far behind (another set of pistons went in, Pro-X pistons had collapsed skirts but much sooner than OEM).
Somewhere in there the original flywheel came apart and took out the stator. This was warrantied. 2013's had bad flywheels, so be aware of that when shopping. Flywheel comes apart and kills the stator. New OEM parts are expensive for this. This would have me going for a '14+.
I clean the clutches about every 500 miles, replace bushings/springs/sliders as needed. Doesn't eat belts. Mostly gas/oil/go. I'd buy one again. Mine is now essentially a T3, would recommend getting one of them right off the bat.
Biggest complaints: bars are too tall from Doo, skis are not my favorite, and running boards are terrible. Drop bars, Polaris Gripper skis, and install aftermarket boards, great sled.
As miles go up, shocks will degrade. Shocks on a used SP are throw aways (cannot be rebuilt); so get an X package if you can, they can be rebuilt reasonably priced.