This is a good question.
I like to think that the M60 are an excellent quality speaker and as long as you take care of them (no amp clipping, free of moisture, etc) they should last for a few decades at least.
I would bet that you would have cabinet issues (seems coming apart) well before you have driver or crossover issues.
There used to be an issue with the foam around the outside of the driver disintegrating, but Axiom's new drivers are now rubber instead of foam. New meaning 1999 through today
My AX2' sound as good today as the day I bought them in 1986.
