Do bags of fertilizer get old?

A store was going out of business, so I bought 2 years worth of the
fertilizer products, the kind that comes in 4 different kinds,
numbered 1, 2, 3, and 4 for spring, early summer etc.

I've decided not to use the stuff, so I want to sell it or give it
away, but I don't know if it is still worth anything.

Grass seed gets much older and less viable every year, but fertilizer
and crabgrass killer don't have to germinate.

So how good are these products 3 or 4 years after I bought them?

Thanks.