We went to one park in the morning ... MK, EP, or HS. Usually for 3-5 hours. We usually then took a break.
In the evening, we often drove over to Animal Kingdom for an hour or two. You're so close to AK, it is really easy to pop over there for just an hour or two. We were able to do all the stuff we wanted to do at AK all in three evenings and didn't need to spend our morning time there. If you have park hopping abilities, this is a great option.