you are dead wrong buddy, double clutching will only prolong the life of you tranny and clutch because your clutch won't slip as much on the flywheel. Brent is right if the fly wheel is spinning same speed as clutch it won't rub together as hard. Now does you clutch like you riding it and slipping it like that no, double clutching makes it easier on your driveline. What they said in fast and the furious is a bunch of bs I'll admit that because you don't double clutch on an upshift.

But double clutch is a racing technique, I have been double clutching and heel and toeing ever since I learned of it on the 2GNT page and my teacher taught me. Basically it's a smoother way to down shift, I don't know what brent was saying about needing to do it with a lightened fly wheel though. Double clutching makes downshifting smoother, you rev match the engine to the clutch (I forget it's the two different moving parts). Which doesn't make your car jerk or upset the cars balance. So when you double clutch the car doens't bolt back and just keep on accelerating. It would be useful for downshifting on a straight or highway battling. I've heard you can mess up your syncros from a post a LONG time ago but mine are fine after like a million double clutches. There are two way to double clutch and it worx either way.

Clutch in (single clutch)
Shift into neutral
Clutch out
blip the throttle to rev match (rev match as in match the RPM to how fast you think you'll go when you downshift you kinda just feel have to feel it)
Then clutch in (double clutch)
and downshift into lower gear
clutch out
and apply throttle
(this way I heard is for old cars that you couldn't apply gas and downshift at the same time, I used to do it like this)

other way:
Clutch in
Shift into neutral
Clutch out
blip throttle and revmatch while clutching out (kinda like slippin the clutch)
and apply throttle as your letting clutch out

Don't say double clutching is pointless because double clutching is an advanced driving technique that road racers (like me) live by.

Heel and toe is an even faster way to downshift and revmatch but I won't get into that.