I don't know about the low V.O.C. environmentally friendly varnishes, but the old stuff does not go bad in a sealed can. I have used old varnish that was heavily crusted over, and I used an unopened quart of Sherwin Williams Spar Varnish that was at least 40 years old, and they set up perfectly.

I have yet to see an expiration date on any paint, stain, or varnish product. But I am not impressed with any of the newer low V.O.C. finishes, and prefer to stock up on the old stuff when I can find it.

A true sign of mental illness is any gun owner who would vote for an Anti-Gunner like Joe Biden.