How many miles would you change your timing chain on, some say they have done 80,000 miles on the original belt what's your opinion? just to ease my brain as had xt 350 many moons ago and the cam chain tensioner slipped and put the valves into piston, only needed valves, regrinding and tensioner but still plays on my mind (as tensioner was self adjusting I think it reached the limit and the stretched cam chain put pressure on it to slip and put valves into piston it was my first enduro bike at 16 and would not like me to make same mistake)