Depends on the bike, I'd think....
I would not expect excessive wear for Bike Fridays, Swifts, Bromptons. I'd still check those bits every now and then.
Dahon, Giant Halfway, Downtube and others require a little more attention. For example, the hinges on my Dahon get a little loose on a regular basis, even without folding / unfolding the bike. But as far as I can tell, the mechanisms itself should last about as long as any other moving part on the bike.