When I was doing my homework for the anti-freeze update I sent in to the magazine I think that I saw somewhere that the old-type anti-freeze did have a shelf life. I'm not positive, but I think I read somewhere that one of the advantages to the new organic acid technology (OAT) anti-freezes is that the OAT anti-freeze has a much longer shelf life. The numbers that stick in my mind are about five years for the old-style anti-freeze and 15-20 year shelf life for the OAT stuff.
I'm not willing to do the Internet searching to verify that, but the Valvoline site may lead you to some information on the subject. You can also call or e-mail their technical people with that question.
That said, I agree with the previous comments on improvements to anti-freeze. I don't know how much you mind changing your coolant, but I consider it to be a major nusiance at best. I have installed an extended-life anti-freeze. It's an OAT type and can be renewed by merely adding a pint of extender fluid. It will go three years or 300,000 miles before requiring the extender. Then it can go another three years.
There are several brands of extended-life anti-freeze available, but the only brand that I could find extender for was Caterpillar.
Data:
Caterpillar Extended Life Antifreeze/Coolant (concentrate): 119-5150
Caterpillar Extended Life Antifreeze/Coolant (pre-mixed): 101-2844
Caterpillar Extender for above Antifreeze: 119-5152
I used the pre-mixed. If you use concentrated OAT anti-freeze (anybody's brand) DO NOT USE TAP (CHLORINATED) WATER.
Loren