compression test is not the answer
It seems to be a big misconception that just because the sled has over 100lbs of compression it doesnt need rings. Lets think about this, a 2 stroke motor takes 2 times the abuse a 4 stroke does, not to mention that piston ring seal is critical to performance. You need to do a leak down test in order to know if a motor needs rings, the amount of pres. lost in a cylinder thru leakage past the rings/piston skirt is far more important then the amount of compression it can build, but lose very rapidly. The pres. you lose past the worn rings/piston skirt is pushed below the piston and contaminates the fresh fuel/air charge in the transfer ports and crankcase. You can see this on a engine as black residue on the bottom of the transfer ports on the cylinder and on the pistons sides below the 2nd ringland, it will be all black. I have seen engines with as little as 1500 miles on them need rings, and then I have seen some with 5000 miles that are still pretty decent shape, all depends on oil run and what kind of conditions it was used in.
The second part of this pertains to quality of the oil used, if you use nothing but yamalube or some other just so so oil, your gonna need to rering the sled more often, the snowmobiles of today are leaps and bounds above in power output what they were in 1978, and so should the oil protection you use. You cant beat technology, 100 percent man made synthetic oils out do petroleum based oils 10 to 1 no question about it. If you take apart a engine that has run yamalube its whole life you will find a dry, baked appearance on all internal parts, lets take apart a engine run with amsoil or another quality oil and youll find a nice sticky oil coating and almost no signs of wear.
In closing, a compression test is a tool, but you need to use the right tool to complete a job. If you want to know the condition of the rings, a leak down test is the tool to use. If you have over 3000 miles and you have run so so oil, you most likely need to freshen up the engine, even though it still starts up fine and runs good. There is lost performance waiting to repay you for your efforts.