Your clutch will be complete toast when you try to accelerate from a standstill and your clutch is not providing any friction with the flywheel, therefore not a lot of acceleration will be going on. Trust me, when your clutch is toast you will know it.

 

It is related to your syncros, however, if you could somehow perfectly rev match on both the upshift and downshift you would only wear your clutch on the initial take off. Although it's tougher to do in the S, in my 1990 Legend was very easy to shift both up and down without the clutch. Just a matter of matching the engine speed to the transmission speed (rev matching) and I could literally drive all around without using the clutch. Of course, I'd have to do a rolling stop, but I could still do it.

Getting back to your original statement, if you use the engine to slow you down, but you don't rev match, you are, in essence, reverse slipping your clutch and over time it will affect its life.

How hard the car is driven absolutely does affect how long it will last. That 90 Legend had over 220K miles on the original clutch.

My MY00 S2000 has 29K miles on it and doesn't have any problems with the clutch. However, I have never done any 6k clutch drops or anything. My car has been babied.

 

My clutch was just about done ar 40k and then I replaced it with a Competition Clutch stage 2 street disc and PP