For us, 8 days is perfect.....and that's 8 days not counting travel days. With 8 days, we can do 2 days at MK, 2 days at Epcot, and 1 day each at DHS and AK. The remaining 2 days, we'd be mostly at the resort, with a short jaunt back to DHS and/or AK for things we missed or want to do again.
What would your perfect day at WDW involve?