> ive never seen the closed-cell dense foam inside a schoeps box break down
That material should outlast--well, me for sure. On the other hand, if I can say this without starting a panic--there were two distinct types of older Schoeps boxes with "blue suede shoes" exteriors, one of which had slightly-quasi-furry, royal blue inner linings that would eventually shed tiny, sticky particles. The other type of blue case had the same dense, closed-pore plastic of which you speak, though--which of course is perfectly fine. So you can't judge a blue Schoeps case by its cover alone. Still, I wouldn't advise people to use the type with the plush interior for any long-term storage. To the extent that I had those, I've replaced them with newer types, and in one instance I brought a BLM 03 C to Schoeps for cleaning on account of the residue.
> ive seen several spongy windscreens fall to bits
Me, too--and before they get to that degree of decrepitude, they're already shedding small particles. Please bear in mind that condenser microphone capsules work on the same principle as electrostatic air cleaners. Trying to prolong the life of a foam windscreen or pop screen beyond its limited span of years is a false economy. If you take a foam windscreen or pop screen and drag it on a piece of rough, white paper and it creates a visible dark streak, replace it. If, however, a genie appears instead, make three wishes and please consider having smooth, peaceful elections this November be one of them.
--best regards