Air kills cartridges?

Rubber suspension components deteriorate, primarily because ozone attacks rubber. This is oxidative deterioration. Rubber also deteriorates beause of crystallization, causing it to lose flexibility. Cold storage impedes oxidative deterioration but accelerates crystallization. This low temp crystallization can generally be reversed by heating though.

I have four cartridges in current use -- ADC, Grace, Pickering, Ortofon -- that
are at least 30 years old and sound great. Suspension deterioration is
overexaggerated as a issue, IMHO. In a couple cases where there seemed to be
a problem (including one of the four mentioned), I was able to bring them back
to life by applying a tiny amount of Rubber ReGrip to the suspension with a
toothpick. I'm sure that some carts do expire from old age, but I wouldn't
hesitate to buy an elderly one and I sure wouldn't keep them pickled in some
kind of chemical bath. I do live in a moderate climate, so that may be a factor
to consider.

Dopgue is right, the deterioration issue seems to be exaggerated often. I too have cartridges 30 years old that sound fine still. Another good product is "Rubber Renue" by M.G. Chemicals (mgchemicals.com.) I've never tried it on my cartridge suspension, but it works great on grommets, gaskets, belts, etc.