AP's are good for one year after the first time you actually use the pass at the park not on the purchase date.
We became unexpected AP holders this past Oct.
We purchased 10 day no expiry/hopping tickets from an online retailer last summer for our trip in Oct. We planned on using 5 in Oct. and save the rest for another trip. This was before the price increase for Disney tickets in August and the online retailer offered the tickets at a great discount off of the WDW online and gate price for the same ticket. Long story short, I heard/read something that led me to call the WDW ticket center before our trip and they informed me that no matter what I payed for the ticket or the fact that I bought it from an online discount retailer, WDW would give me credit for the gate price of each ticket toward an AP. BTW- the ticket we bought now cost more than an AP. Anyway, they did and I got 4 AP's and a refund of $24 and change.

No questions asked.
Downside, they expire. Upside, 3 GREAT trips in one year that are memories my children will never forget!
We live 500 miles from Disney and camp in an Americamp 5th-Wheel.
We have used our AP's 2 times and have one more trip planned for this August before they expire.