Atrictly speaking, resort parking is for resort Guests only; anyone else, such as those dining at the resort or just having a look around, are limited to 3 hours. This is to prevent locals and off-site Guests from taking up all the parking spaces, making it more difficult for those who are paying to stay there to get a parking space.
The Epcot resorts are not as strict on this parking time limit as the monorail resorts, but any time you park at a WDW resort and leave your car more than 3 hours, you run the risk of having towed.
However, they are not so strict on the time limit if you valet park, so if you're going to be touring WS for a few hours before leaving for the airport, you can valet park at one of the resorts.
If you're going to be in the park all day, then you're going to have to move your car to the Epcot lot after breakfast.