Who knows, unlike others I've never really tracked how long parts last on my bikes, though I do think modern bikes need a little more fettling time with hydraulic brakes and suspension etc.
I was pondering about the state of my bike yesterday though on a long ride, currently the Kona has a number of ailments that I've neither the money or time to delve into at the moment, It currently needs:
The bearings in the freehub are running rough and need replacing.
The left hand pedal bearings need replacing.
The tires are at the end of their life and the sealant needs topping up.
The gears are not indexing crisply, especially downshifting.
The brakes needs bleeding.
Bottom bracket needs looking out, bit of a clicking/creak emanating from that area.
Due to summer plans, I'm prioritising keeping the mountain bike in tip top shape and there is one component there that is time dependant on maintenance and that's the front forks. To that end I've just done a 50 hour lower leg service and later this year I will give them a complete strip down and perform a 200 hour service. I've just replaced the tires on this one as well as bled the brakes and replaced the bottom bracket. The pedal bearings are a little rough, but otherwise this one is in good nick. I've ridden about 900 km so far this year on the mountain bike and probably spent a few hours fettling it.