How long does paint last in can

That's a tough call Ratso, especially without knowing what primer it is. It's an on the spot judgment call. I would tell you no off the top of my head. I can tell you that if it's bad, and say never dries properly, it's going to cost you a lot more than the 10 buck cost of a new quart to fix.
A vanity should get a coat of bonding primer. Go to Home Depot, or the local hardware, and get a quart of Zinsser 123 latex primer. Better to be safe than sorry.

Why take the chance?

4 years in storage, go get some new paint.

4 years isn't that long assuming it was stored where it didn't freeze or get too hot and the container was sealed up good.
I've used paint and primer older than that (much older).

I have had paint last 10 years and still be good and I have seen it go bad in as quick as 2.

Matthewt1970 said:

I have had paint last 10 years and still be good and I have seen it go bad in as quick as 2.

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That's exactly what I was going to say in response to wrongdave, it's a crapshoot. I might have used it, but only after I looked it over well. I used an old BIN can once and it took about 5-6 hours to dry, and it was making me real nervous. I wouldn't want to responsible to OP if he had a problem with it and I suggested he use it. It's kind of like a "don't do this at home, these stunts are being done by professionals" thing.:laughing:

JS- everything working? (nothing to do with thread btw..)

Brushjockey said:

JS- everything working? (nothing to do with thread btw..)

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Not yet. Sent you a pm.

Paints and primers (especially with the low-VOC technology and content at present time) do not have the same freeze/thaw resistance as the products in the past. The general label storage directive is one year minimum, unopened, where it used to be probably 2-3 years. It depends upon how the can was resealed, and where it was stored. Stir it up, make certain that it smells OK. Solvent products can be tricky, although latex/waterborne paints are pretty obvious.

I have had paints last 20 years- others went bad in 6 mo.

Open up and stir- the smell test is a good one,if it is funky- don't use.
And if it is like cottage cheese- it froze.

And floating green/black stuff is not a good sign...