We get APs every year and never renew within the window, although we do buy the vouchers. If you renew, your expiration date is the same as the original AP, just one year later.
If you wait to activate your voucher on your next trip, then it is good for one year from the date you activate.
We find that by not doing the renewal, every 3rd or 4th calendar year, we get by with no AP expense.
This year, we will activate in Dec. and have trips planned for Dec, May, Oct/Nov. No AP expense in 2004-yipee.
Next trip after those are in 2005-we will buy vouchers then.
But, this works for us and may not work for everyone. But, it you dont go very very frequently, I would consider not doing the renewal and just waiting until your next trip.