Provided it was broken in reasonably & that the factory parts are all up to specifications & the bore isnt at the bare minimum allowed & piston at maximum,( I think someone had a problem & on teardown, which followed immeditaely after "Tear UP", that's what they found), well, what I am trying to say is, IF all the stuff in there is the way the factory wanted it & you take care of it well, you will ride it for years, learn how to do basic maintenance, progress to doing things that will scare the heck out of ya, make friends, have fun & be glad you bought it. Take the riders course, buy a manual & have fun. The work you do will more than save you the $$ you spend on tools.

It's an simple engine, and almost old school.

With old school come the need to be diligent on the standard periodic maintenance.  Oil changes, valve tappet check etc etc.

But,  if maintained, and you drive realistically (no 200 yard wheelies ), it  should go years.  

I have no idea.  I have a 2000 Savage and I overhaul it every year

I bought my 2002 LS650 new May 2002. I keep it in my garage except when I ride to work. The bike has 7300 miles on it. The milage is light because I ride a short distance to work and run local errands. I've done some work on it to get better sound and performance. I use Amsoil Motorcycle 10w-40, changed every 1500 miles with filter. If I don't make 1500 miles, I change the oil every year instead.
I have observed no degradation in performance, no leaks, no oil consumption, no final drive problems, no brake problems, no electrical problems. I've had to replace the original tires. The bike lives in Central Florida and ridden all year.
I'm really impressed with the reliability of this bike.
I believe the bike will go happily by the 25,000 miles without major maintenance. Keep good records, inspect/maintain your machine often, and use excellent lubricants.
I suspect Savage_Greg puts 25,000 miles on his machine every year, so he has to do major maintenance more often than most of us.