My experience is that Harley V-Twin motors that are keep relatively stock will run for years if you take care of them. However, keep in mind that the basic design for these motors dates back to the early 1900's, and when you start increasing the duration of the valves, increasing compression ratio and run at high rpm's, the reliability starts to go south. (I know this will get the mail goin!)
Jake, we must be related
I agree with you 100%. If you want the engine to last leave it stock (Inside) and add some fuel. Stage 1 is OK too but when you open any engine up after it leaves the factory and add cams, heads etc, there goes the reliability as well as a long engine lifespan.
It's like the wear factor increases once the engine isn't stock mainly because of the way it's ridden. Who is going to invest in engine work and not utilize the extra power?
Nothing like a stock engine for a good long life!