All foam deteriorates over time as far as I can tell. I've had DPA, Neumann, AKG, Windtech and Schoeps windscreens. All of them showed signs of deterioration, the schoeps in about 1 year. It starts with seeing black dust if you thump them. That black dust can become charged and stick to the capsule and gunk it up. I would imagine pelican foam would do the same thing especially since when you pull it apart it kind of shreds. I previously kept my caps attached to the Nbox actives and in B1 windscreens inside film cans. When I noticed dust I started storing them in the vials. Since I rarely record these days, I just attach them before the show. I haven't noticed dust from my Schoeps B5D screens or Shure 81s FWIW, but I'm sure they degrade as well.