Just know that if you renew your APs online, it will not save you a trip to Guest Relations to have them validated. What they send you is a certificate which must then be turned into a real ticket. Once you do this, you are good to go. The shorter lines are usually at Downtown Disney Guest Relations, so if you have the chance, try to stop in there the night before, so you can expedite getting in the parks in the morning. They can renew your existing AP there, as well. You may renew your AP for the discounted price up to 30 days before or after the expiration date, and the expiration will revert back to the date the previous years expired... so if your ticket expires on Nov 20 this year, if you renew, it will expire Nov 20 next year, as well. If you renew ahead of time, you will use your current AP until the renewal date, at which time you will begin using your new one.
Hope this helps!