I have a 99 softail with 50,000 miles at what point should I consider rebuilding the motor? She runs strong now no issues. Just preventive maintenance.
I owned a 1999 night. train. At about 20k miles I bored out the top end and new Hi compression pistons and V&H two into one with a tuner. That is all at did to it the whole time I owned it as far as engine upgrades. At 147,400 miles my lower end took a crap. So to answer your question, your engine will last as long as you don't mess with it too much and keep the maintenance up. That Evo was one hell of an engine. And by the way, I sold that bike with the blown engine for 10,000 after owning it for 8 years.