How long a clutch lasts depends entirely on how well you manage a manual transmission. I had a clutch go beyond 200,000 miles in my first E36, and I'm at 150,000 on my second E36.
Whether or not the flywheel needs to be changed also depends on your management style. I did not need to replace the flywheel at 200,000 miles. I gotta back off on that, I do not recall that I had to replace the flywheel, and I paid a shop to do the work (which I almost never pay for work to be done because I do it myself). I do remember that the parts and labor was about $875 for the work that was done.
If the transmission is down for any reason, it makes sense to do a pre-emptive strike and replace the clutch, but clutch work is not on the preventative maintenance schedule -- there is no guideline that says, do this at a certain number of miles or years.
JPButler is describing a problem that I believe is associated with the clutch master cylinder. He cannot select the gear he wants unless he releases the pedal and applies it again. This is the Clutch Version of a failed master cylinder. When the Brake Master Cylinder starts to fail, the symptom is that your foot sinks slowly to the floor as you wait at at traffic light or other location where long periods of holding the brake pedal is necessary, you recover from this by pumping the brake pedal a couple of times before you eventually replace the brake master cylinder. When the clutch master fails, the result is that gear selection can be a struggle, and you recover by working the clutch pedal a time or two until you replace the clutch master cylinder.
What happens in both cases is that there is fluid that is moved by a piston that is connected to the pedal. There are o-rings that keep the fluid in the channels that it is supposed to be in, and these o-rings seep and allow the fluid to move around the piston and this makes the pressure applied on the system go away, the system does not work and you have to pump the pedal to bring the pressure up again. This is called, a leaky master cylinder. Although there is no external leak where fluid will be seen on the outside. The leak is entirely internal.
Last edited by jdstrickland; 10-05-2012 at 12:00 PM.