Are NOS phono cartridges best avoided?

I have read that the compliant suspension components in phono cartridges are subject to deterioration/hardening as time passes. Is this strictly a function of time or does exposure to atmospheric conditions and polutants factor in significantly? I occasionally see "new old stock" cartridges for sale/auction that were good performers at the time of manufacture 10-20 years ago. Are these best avoided or are they still useful if they have been sealed in factory packaging? Anyone have experience with this sort of thing? Thanks, Will.