I'm not understanding the time issue, but AP's can also be bought on line.
And seriously, it doesn't take any longer to buy them at the gate than it is to pick them up. Maybe a few extra minutes. But we are FL residents, so they have to go and verify everything.
Not sure why one would buy an AP and not use it for several years. The savings isn't significant enough over price increases to freeze that amount of money in a non-sellable, non-refundable asset.