I don't have a 2 stroke either. However on my 4 stroke Robin Subaru 35 I have 4405 hours of use on it. If you figure an average speed of 15 mph, that'd be 66,075 miles.
With 4 strokes regular routine maintenance is the key to longevity. I change my oil every 25 hours of use and clean the air filter every 10 hours of use. I change the fuel filter once a year.
Additionally I also use a tachometer and have a shift kit. This way I'm never over revving my engine or putting it under engine strain.
I do carry a spare carburetor due to E90 clogging up my jets. So when that happens I have to clean the clogged up one.
Still the only thing I've ever had to replace is fuel filters and spark plugs.