I commuted most days for 28 years with weekend rides, about 2800-3200 miles a year. My 1997 Mountain bike (bought new) still has the same drive train but the chain gets replaced every 3000 mile or so. My 1984 Road bike (acquired in 2009) seems to need a chain about the same amount, and the rear gears needed replacing after about 6000 miles.

My 2015 semi-touring bike went through the original chain after only 1000 miles, plus the rear gears after about 1500 and the rear wheel hub was trashed after 2000. The new rear gears and wheels are much more robust.

The 2015 bike's 'brifters' also seem to chew through shifter cables much faster than the others. The 1997 bike used to eat through shifter cables quickly when it had cross-fire shifters, maybe once a year. I converted it to drop-bars with thumbies near the bar-ends a couple of years ago and there is no indication of wear.

I may have changed the cables twice on the down tube shifters on the old road bike since 2009.