Actually MK and Epcot are the only two parks where I do spend a whole day at each. DHS and AK just dont have enough to make me want to stay. AK and DHS usually take just a few hours, 3 or 4 at the most. Park Hopping is fun though, epecially if you just want to make a quick stop to do one or 2 things. The last day I was there we wanted to see SSE one more time. So we parked at MK and took the monorail to Epcot, rode SSE, then actually went to the UK once more, got back on the monorail, and switched to the MK one.
When we do DHS and AK, we usually end up going to 3 parks! We do AK then DHS then in the late afternoon/evening usually head back to MK. A little tiring, but I dont mind it