Yes.
You'll pretty much pay for the annual pass after two trips. I think the math is that a AP is less than $100 more than a 10 day ticket. So if you are going for 5 weeks you have more than paid for the AP.
Plus 5 weeks worth of discounts might pay for the AP as well.
10% off most resturants (although you might do better buying the TiW card depending on your eating style, it's an extra $100 but you get better food discounts)
10% off merchandise
10-20% off tours
Plus if you happen to luck into any AP Room Only discounts at the Resorts.