From what I've read over the years, the stock clutch is just fine for nearly all stock/mildly modded street applications.
Highly modified cars need more sticky and less civility for drag racing, so they generally opt for the aftermarket kevlar type clutches and they have to change them regularily.
If after reading Marc Haibec's write up you still have questions, contact Bill Boudreau, "The ZF Doc".
http://www.zfdoc.com/