I don't know about forever but I've never had a failure but I did have a fouled a plug.....twice. My 2 - 01 700's ran great for 5 years, then 05 600SDI 4 years, 06 800Ptec 3 years and 08 800R 1 year. All mountain riding. The 700's are sold now, the 600 to follow this year to make way for a new 800R. Maybe someday I'll be a statistic but untill then I'm just another happy customer as are the majority.