I've found that generally speaking the open cell foam (usually white) that comes with many types of tires will often break down with water and especially with tire compounds. The Closed cell foams don't seem to break down as quickly if much at all. Seems I usually wear out the tire before the foam. I'm about to cut open my first few sets of tires that are worn out and see how the foams are. That being said I don't usually go saucing my tires unless I'm planning to hit the track the next day. Sometimes I will double up on the sauce if the tire feels like it has hardened up a bit due to age. I've also noticed if you leave your tires out of the bags for even a couple days they will usually get a bit harder. Hope that helps!