I have two pair of JBL 4411's that are the same age and have been in the same environment all their lives. Two of them have rotted foams around the driver and two do not.

I am planning to repair the foams on the two with repair kits. The question is: Are the other two fine if they haven't rotted yet, or are they just days away?

Is rotting foam an either it is or it isn't or are there degrees of rot and then at some point it becomes visible.

If the others are right behind, I might as well repair them now rather than do two today and two more next month or next year?

Thoughts for a newbie?