Hi Kimberly,
I am completely envious of your 17 days at Walt Disney World! The ticket with the most days of park admissions is ten days. After ten day ticket, it becomes more cost effective to purchase an annual pass than to add another multi-day ticket.
When you are making this decision, I would encourage you to really think about how you are going to spend each day. You have 14 days from first use to use your ten day ticket to visit the parks and water parks. You could spread your park days out and mix in days where you just visit a water park. You could have a combination resort day/water park day or split a day of shopping at Downtown Disney Marketplace with time at a water park.
If you are certain you want 15 days of park visits mixed with water park visits, then the
Premium Annual Pass is actually cheaper. A ten day ticket with the park hopper and water park fun & more option plus tax costs $484.58. A five day ticket with the park hopper and water park fun & more option plus tax costs $431.33. If you add those tickets together your total cost is $915.51. The cost of the Premium Annual Pass with tax is $829.64.
While either option is expensive, the
Premium Annual Pass also offers a variety of discounts that might help offset your costs.
I hope I've helped with your decision-making! Please let me know if I can help you further with this question or any others you might have!
Wishing you a magical vacation,
Amy H