I wouldn't suggest saving MK for night. If your going to take the park close advantage, I would do it for AK. I'm an annual passholder, and we are constantly doing park close at AK. We normally get there around 3 and finish the park by 7, sometimes even earlier (Always save Everest for night, theres always a posted wait of like 20 mins, and ends up being a walk-on). I know with DHS it's hit and miss. There are times the wait dropped and we were able to get a lot done, and other times the wait stayed about the same until the last half hour. I think a lot of it has to do with park hopping and capacity. People make reservations for say Epcot and AK, go scan in at 1:50 so they can go to DHS / MK at 2 if there were no reservations left. I've also noticed sometimes there's a 1:30 to 2:30 dip. People who are either going to lunch, or back to the hotel, or park hopping. A few times when timed right we were able to get a lot done then too. I would say keep your eye on the app and wait times a few days before you go, and you'll notice some trends that will help you figure out the best plan. Have fun!!