About 3 years ago, my brother-in-law's brother and wife gave us an exercise bike which they were replacing with a more up-to-date version. At the time, it's speedometer indicated about 300 miles. It is a totally mechanical bike, with an adjustable tension roller pressing against the wheel, which makes it possible to simulate mountain "grades" and, if adjusted properly, will make us work hard. On the days when weather or a particluar time commitment prevents us from going for our walk, we use this bike for about one half hour - and for myself, I adjust it so that I work up a real sweat. On average, I cover about 9.3 miles in that half hour (according to the odometer). If I do any less, I'm not working hard enough. Both my wife and I are making pretty good use of it, but since she gets quite a bit of exercise around the house, it is I who does the bulk of the pedalling on the bike (90%, or so).
In the winter, the bike is used almost daily. In the summer we're much more likely to walk - our neighbourhood is hilly, and a good walk is good exercise. In any case, the other day, when I was doing my usual half hour on the bike, the odometer turned 3000 miles (it's an older bike, and still calibrated in miles). This means that we've added about 2700 miles (a bit more than 4300km) to its total use. That's the distance from Vancouver, BC (our city) to Halifax on the East Coast. It also means that the bike has been used about 320 times by us (it's getting close to the equivalent of one year's worth of half-hour per day pedalling). I never thought we'd "bike" all the way across Canada - we did it "virtually", of course. Luckily, the bike doesn't simulate any inclement weather "along the way".
The bike works just fine - I've oiled the various bearings, chain, and especially the pressure roller about 3 times. I expect it to last a lot longer still.