Hey there, Cheri!
It's so much fun to visit
Walt Disney World during different seasons. Each season brings with it something new and fresh and exciting to the parks and resorts.
When you think of the times the year that the
theme parks would be open the latest, think of the holiday seasons. The
Magic Kingdom tends to be open latest when the kids are on holiday or summer breaks - much like the other parks. Since you've done Halloween and early summer, I'd look at doing something closer to Christmas or during spring break, when I've see the Magic Kingdom open until 11 PM or midnight many of the nights. You'll also see longer hours over the summer, especially around Fourth of July.
If you are a
Walt Disney World resort guest, don't forget that you can take advantage of
Extra Magic Hours. There's a chance during your stay that the Magic Kingdom will be open even later, and you can really close the place down!
Wishing you a magical time planning for your upcoming vacation. We're right here if you need us!
Anna