I'm "upgrading" my suspension from a Sentra SE springs to Sentra SE-R
springs - I've found a set that a gent has stored in his garage from
1997. I thought I had read somewhere that suspension springs can lose
their ability to lift if stored for a long period of time, and a search
of Google/Usenet doesn't come up with much either way. The springs
themselves look to be in good shape, not cracked or any visible damage.
He took off these springs to upgrade his suspension to Eibach springs
and aftermarket struts.

Is it safe to buy springs stored for such a long time?

Regards,
Neurowiz