I would check with your dealer and see if they have an aftermarket warranty available, I have seen them around 25-3 grand for 4 yrs coverage they are usually much cheaper for the peace of mind, I have seen some sleds have issues early on and some go almost 10000 miles, its a crap shoot either way, all depends on your comfortablility of risk should something break.  For us we buy new with the the 4 year warranty then typically sell them while there is still warranty left on them which makes them more desireable in the used market. 

I guess a good sanity check is what did you pay for the 3 extra year aftermarket warranty on your recent purchase - or included in the price so not really known?   If I had to guess the bad bearing on the older sled covered under warranty would have cost $600 to $700 with no warranty at the dealer (assuming no other damage occurred after the bearing failed) - $500 in labour and $100 to $200 in parts. I think 4->5K is probably a good number for new motor / new rebuilt motor - I am not sure you hear of many motor problems though the last little while with the 850 and not sure there ever was on the 600/650, I seem to recall there being motor mount and bearing issues though (bearing issue might have been caused by the motor mount), like what you had on the POO, but I thought that was resolved. You do hear a lot of folks stating they would never own a 9R out out of warranty as well too  - lots of power being put of that little 2-stroke mill!   Warranty no doubt is a gamble of sorts, for both you and the reseller - I just do not think on a toy, for that amount of money on top of the sale, I would pay for additional coverage....but maybe I would if I was buying a new 2-stroke sled again in the next little while.

I have close to 7K miles on my 2020 850 XC currently that came with the factory 4 year warranty, I bought the sled a year old so had the remaining 3 years on it. I used warranty once on a Quebec trip when the jackshaft bearing came apart on me. I bought a '25 9R XCR in the Spring off the dealer floor & got a 4 year warranty with it, 1 year Polaris & 3 year aftermarket more for peace of mind on trips & the fact that I can't rebuild these sleds anymore. I would guess you'd be over $4k for motors these days at a dealer to either rebuild or buy a new block & install. 

Your case I wouldn't worry about it. I personally think if anything going to go wrong, it would have happened by now. Mines out of warranty too. Between two probably save enough to rebuild one if it ever happened. These engines for two strokes  are very reliable. Not many having trouble besides odd manufacturing defect. 

Wife gave me this for christmas. Testing follow mode.