Freelunch, I have some Schoeps capsule holders (the clear plastic kind similar to what they still use) that are older than the foam in that Halliburton case. They haven't decomposed, but have become a bit discolored. All told I don't think it's a bad idea to replace them every quarter- to half-century or so, if you feel like it.
Schoeps' old (1970s) black rectangular cases, on the other hand, were padded behind the velvet lining with the type of foam rubber that eventually crumbles. I replaced those cases six or eight years ago. Attached are two photos of the type of case I mean (the one shown is a half-width accessory case, but Schoeps used to use full-width cases of this type for CMT-series microphones and the early Colette series).
--best regards