I think this is the longest thread I've started without diving in to give some support. In any case, I suspected that the bottle I found in my company's larder was some I purchased in mid-1999 and left there and no one used it after. I've started cooking with it with no harm and no bad taste, so I consider it 'aged'.
Thanks for the edifying advice and expansion on some collateral themes.

As Robin Williams once said, (as Popeye) "Ya don't have to be a physikisk to know what matters!"