Aftermarket clutches are designed to hold more power, or to engage faster (puck style discs), but they aren't designed to last longer than the stock clutch. The only way they would last longer is if you're making more power than the stock clutch can hold and it's slipping and wearing out faster than usual.
A clutch should last about 100,000 miles with a good driver, even if you drive fast all the time and shift alot.
If you're not making at least 40 hp more than stock, then the stock clutch is fine. If you're wearing them out very quickly, then you're abusing it and you'll need to work on your driving technique so that you don't slip the clutch so much.