Unless you really hammer the clutch, it should last quite a long time. I had mine changed out at 27 years, and the plates were still in good shape, just wanted new ones in there. Only way to tell, is go in and see whats there. If you do like to work the clutch, you can buy heavy use rated plates and springs. (police depts. use them as the bikes are out all day everyday. )
If we are talking apples and apples, the the petcock can go at any time. I can't tell you all the things that cause them to leak, but the newer ones you never even mess with (ie. shut off) except for going to the emergency tank.
I restored my shovelhead at 72,000 miles and the wet clutches were still in good shape but I replaced them just because. Replaced stock petcock too with a Pingel but it was ok too. The whole bike was stock other than regular maint. I replace the piston rings once at about 40,000 miles.
While we have a clutch thread going, and since the original question seems to be pretty well answered,
I hope it won't be a hijack that I have a related but different question.
I just finished putting on the hydraulic clutch conversion on my LowRider, and I really do like it.
Not that the previous clutch action was any big strain, I just liked the idea of there being NO friction,
the needlessly thick cable looked clunky next to another slim hydraulic line,
and I looks of the the V-Rod's symmetrical grips, with the same but reveres image hydraulic reservoirs on both sides, brake and clutch.
Long ago I had the 95" kit put in and that comes with a heavier spring, so my clutch should be at least a little bit stiffer than stock. It's not the race clutch, still just the spring steel plate with fingers, prolly thicker.
But when I have run the bike hard a few times and shifted hard, I thought I felt the clutch slip a little. So now that I've got reduced grip effort, I'm wanting to bump up the pressure a bit more. Are there several different thicknesses of clutch spring plate available?
I don't really want to go Barnett and the race clutch won't work with the hydraulic clutch kit.
Turns out there are two different action rods available for this hydraulic clutch kit. The one for the 6 speed tranny is a bit less than 1/4 inch longer than the one for the 5 speed tranny, which is right for my bike. So, if I found a slightly thicker clutch disk,or even if I used 2 of the softer ones on top of each other, I could probably accommodate the thicker stack of clutch plates and disks, provided an extra 1/4 inch wouldn't hit the outer primary case.
Any thoughts? I don't race or abuse the clutch now, but the Eagle Parts book's dyno chart says I should have about 90 ft/lbs now, and one of the reasons I don't run it is because I think I know the clutch won't take it for long.