Hop age & AA degradation

I've always known that hop alpha acid % will diminish as time goes by, but I never had enough leftover hops to care. Now that I have small amounts here and there, I'm wondering how to do this properly. I searched around a bit and couldn't find what I was looking for, so I apologize if this has already been asked.

I've played around with the hop age calculators in Beersmith and ProMash, and I understand the basics - better vacuum and colder temps means less hop degradation. But, the age has me wondering. Do the hops start aging when they are harvested or when you actually open the pack? I'd think they start aging when they are harvested. That would mean the stated AA% isn't exactly accurate. Is that true? If so, how do you know when they were harvested?

Is this something people even bother with? Perhaps I'm just being too anal.

I have also fooled around with this in BeerSmith trying to figure it out as I keep stock of hops in my freezer. Just as a rule of thumb I try to use hops that have been in my freezer no longer than 6 months. I have been told by multiple people at a couple of different LHBS that hops will keep decently in the freezer for about 6 months before losing major amounts of AA%.

Yeah, it seems like that's the general thought - as long as your freeze and vacuum seal your hops, there's no need to think about it that much unless they are really old.

That's rather different than the results from these calculators show, though. But it is just a model. I'm more inclined to trust anecdotal evidence in this case.