Age of New Heads - Does it Matter?

What kind of heads are they? The design on some have changed a little, but nothing extreme.

Check them over very well for signs of corrosion. If anything looks out of place it would be best to disassemble and inspect them. If there is rust on the back side of the valves you could have some problems? Maybe check for flatness of the HG surface as well? (but I doubt that will be an issue)

As long as they were properly stored they should be ok.