After reviewing a lot of posts and other helpful info I have a question. With the top ends on 250 and 450 four stroke racing dirtdikes lasting 30 to 60 hrs before requiring top end surgery, how long would one expect a K6 to live, on a mix of `spirited street` and 4-6 track excursions per year, without requiring some expensive repairs? I am aware that the singles noted live at max load and high rpm all the time under race conditions, but trail riding with them only adds about twice the service life vs full race conditions. My last bike, A TLR1000, showed noticable loss of compression with less than 25K miles. Thnx for your time. Rob