The stock clutch in my '92 Dyna has been holding 85 hp with no slipping. It has seen more than a few hard launches and full throttle shifts. It's somewhere in the 65,000 mile range.
The stock clutch is over engineered by a bit but it's not a lot. That's why they offer the SE spring setup if you are doing any mods that give you a modest increase.
Even the older Shovel clutches were tough enough to handle 96 inch strokers for daily riders, now if you want to race that is a new question you will find many answers to