Wow, I just asked on Harvest - found some zucchini and yellow squash from 2007, sugar snap and snow peas from 2008, had been in garage (DH bought them and left them out there) all that time, so ranged from 100 (+?) to below zero, I don't know whether I should even try germinating them on paper towels or not.

Never did find the plastic plant tags I know I bought last year.

Rest of my seeds (leftover/saved from last year) have been stored in the fridge, took them out today to start and never got around to it but I will tomorrow!

The first Hollyhocks I ever grew were from seeds that were at the least 6 years old. I have a wonderful hollyhock patch from those original seeds.

After my Castor Bean success, I started dinkin' around with the rest of my old seeds. (all at least 11 yrs old)
I have found that the more firm and substantial they are the better chance of sprouting they have.
Example- None of the little, wimpy, wispy seeds like Marigolds, rudebeckia, Cosmos, etc,... were viable.
Nor were the larger yet lightweight seeds like Sunflowers.
But the really firm, dense, heavy seeds like Castor Bean, Morning Glory, and Moonflower vine still sprouted.
It seems like if it's the sort of seed you might want to nick to encourage sprouting, it has a long shelf life.