Don't have any idea for a number. The only times I've had foil develop holes were where it had been packed in a soft side kit. All the holes formed where two creases met. Anytime the kit got flexed or compressed the foil worked a little bit. If the foil is pressed flat & creased, it will shorten the life considerably. Also remember that aluminum work hardens so repeated folding & unfolding will shorten the life.