Due to time, I have never had a stay longer than 5 nights with 4 and a half days in the parks. I have never left WDW feeling like I had truly experienced everything and had the "full" Disney experience. My trips always are beyond rushed, with 13 hour days in the parks, hitting 3 parks each day, Fastpassing everything possible whenever possible. I have never once seen a parade or firework show.
In fact, my first trip was 4 nights and only 3 days in the park, and then an hour the 4th day before having to leave.
I guess thats the hang up when you are 17 and go with the parental units who pay for everything and aren't super Disney-freaks who will stay longer. Hey...I guess I shouldn't complain though.
Point being, I have never done a waterpark, taken an afternoon to just hang at the resort and go in the pool, taken an afternoon to visit other resorts, or quite frankly, ever had a Disney day where we weren't up at 7:30 to get to the parks and then in at 10 completely trashed. We always spend a few hours one night at Downtown Disney (except one year we stayed at the Courtyard by Marriot right at DTD and then we went every night)
I would give anything for a full 7-10 days at WDW. I would love to have a day to tour and walk around other resorts, appreciate the resort I am in, hit a waterpark (I love waterslides), head to Downtown Disney for a trip that isn't running around because its so late and we are dead tired, and to see it in the daylight.
So, if time and money permits, stay for a long time. The "long weekend" approach just isn't enough time. But, as is the case for us, it's still better than nothing, and I would take it any day (or in my case every year...lol)
Have a great time!!!