If you keep up the maintenence, almost any new 4 stroke will last you a while.
Fresh oil, filters, valve adjustments, and an occasional top-end will keep em in fine condition.
Of course this depends how you ride too.
If your just playbikin', your macine will last longer.
The harder you ride or race it, the shorter its lifespan will probably be.
New MX'rs arent designed for exceptionally long lifespans though. Theyre designed for high performance use.
The Xr650 or last gen XR600 are better bikes to bet on to be surviving (if not thriving) 5, 10, or even 20 years down the road.
Ive got an old XL500 that is on its first over piston, cases have never been open, and is pushin almost 27,000 mostly offroad (fun) miles.
Show me an MX'r that can do that! :worship: