I just wanted to post my opinion on this subject, altho i am by no means an expert on centrifugal clutches.
I think it all depends on the type of clutch it is and what materials are used.
Like, if it's an old belt style centrifugal clutch (like what used to be on old rupp minibikes and snowmobiles) it will probably last a long time.
if it's a moped / scooter style ( or drum style clutch with friction pads) i don't think it would last as long because the friction pads will wear out and the spring or springs can get weak.
of corse, on an old style belt c. clutch, the belt will eventually wear out, but there are less moving parts, and probably less heat than in a drum style c. clutch.
Heat is a clutches worst enemy.
again, i'm by no means an expert on this at all.
I'm sure that both styles of clutches have decent life spans, but i think a drum style would wear out sooner than a belt style would.
and then of corse, figure in the quality of the components used to make the c. clutch for m.b.'s.....the parts are probably not the highest quality.
just my thoughts.
a belt style centrifugal clutch:
two different drum style centrifugal clutches: