I've always been bothered by the fact that foam dies in cases. I mean...why? Don't give me that "it's because it's old" excuse. I've got my uncle's old reading chair and its foam is in nearly perfect condition after 40, maybe 50 years. So what is it with the foam in cases? This has always been a sore spot with me because it doesn't seem like it should happen since nothing else with foam (e.g. furniture) gets goofy.
Okay, here's my hypothesis--it's because the foam in the case is in an enclosed space. The plasticizers that keep the foam soft and pliable outgas but don't have anywhere to go so they attack the foam. Why would the plasticizer attack the foam that it just came from? My guess is that it...oxidizes, perhaps?...after which it has different properties and becomes a problem.
I attempted to engage the folks from Anvil Cases on this and got the distinct impression that they're rather sensitive about the topic. I never got a reasonable answer. Never got an unreasonable one, for that matter. They just didn't want to talk about it.
So...I'm proposing an experiment. If someone has a new foam-lined case, or perhaps one that's been recently refoamed...try leaving it cracked open a little for ventilation. Granted, my experiment will take ages (read: years) to produce results, so it'll be a while before we know anything, but we might as well start now. I've got a bass case that needs new foam (which is why I was in touch with Anvil), but I haven't gotten around to doing the foam yet because I don't really need it since I'm not playing out. Once I get around to refoaming it, I'll leave it maybe 1/4" open, just for circulation and that will give me another data point.
P.S.: Oh, and what sort of foam are you guys using? The stuff that's available around here in fabric stores is waaaay too compressible and would provide no support whatsoever for an instrument. It's just not firm enough.