Sled repair

[Old Hubbard Rd]

I own 2 Polaris Indy Trail 550 or 500 not 100% sure. They were purchased new in 2000. One sled had about 1200 miles when a blew a head or piston. The other just happened with 2600 miles. What am I doing wrong?? I have owned other sleds (Yamaha Exciter) that I treated like crap and the thing always started and ran. These I treat so damn good. I just had them in at HK Power Sports in early January for tuneups etc. Spent almost $600 on both sleds hoping to have a nice riding season with no issues. I have noticed that each of these sleds are missing their top end. When I start them I can get 70 mph out of them but after rider for a while I notice top end is only 55-60 MPH. I do notice a bogging feeling at that high end after riding for some time. They are both air cooled which could be the problem. I have always used liquid cooled sleds. I'm getting old and I though my family would ride with me so elected to go to family style sleds. I was headed from Meredith to Alton Bay when I blew the head or piston on Fishing Derby weekend. I was riding it hard across the lake. Each time I blew the engine it was driving on the lake. Never have I had problems on the trails. I think the fact that on the trails you are throttling up and down therefore ingecting more oil into cylinders as when your on the lake there is less throttling. Let me know your thoughts and I hope HK gives me a reasonable quote for repair or where would you bring for repair?? HK mentioned that it could cost upward of $1500 although I gave them permission to break it down and give me a part list quote. Oh well!

P.S. Can't wait to get all the replys about buying another brand sled