I've often thought about this. Then you've got the possibility of aged shutters which have drifted or become more erratic. But I simply grab a Calumet electronic shutter speed tester and test at all the speeds, at those actual apertures I'm most likely to use for that particular lens, and with multiple readings each instance to give me an idea of consistency too. I record all that for each lens; and if there are any significant errors, put a little note on the lensboard itself. But other than the highest speed setting in each case, it's remarkable how close all my shutters are to what they're supposed to be at typical usage apertures of the specific lenses involved, and how consistent those respective speeds are. Guess I have it easy, since I don't have anything older than a Copal 3S, and the rest are modern Copals.

So far, no rude surprises for me, even with fussy color chrome exposures. One more arcane "what if" which, for all practical purposes, I can ignore.