Always!!
I specifically insist on staying on property because I refuse to give up EMH. I don't bother with the crowd calendars, EMH are what drives our plans - and pretty successfully over many, many trips. Gosh, how I miss $10 E-ticket nights at MK!!
But, as others have said - EMH plans work most successfully with park hoppers. The mid-day break is crucial to avoid the crowd inflation that EMH brings to a park.
We ropedrop the EMH morning park. No fastpasses - we plan on leaving sometime around noon, sometimes even earlier depending on which park, how the crowds and wait times are building, and everyone's mood.
We go back to the hotel and decompress - and if the weather is good, that's done in the pool.
We go back to a different park in the evening (the time usually depends on what time the park closes) - the 2nd park of the day, is the one where we scheduled our fastpasses - this works whether we are going to a EMH night park or not.
If going to an EMH night park, in my opinion to make it work, you MUST NOT use your FP+ in the morning, but have them scheduled for the 3-hours prior to the start of EMH night hours. This ensures that even if the crowds are on the unmanageable side, you experienced 3 attractions that were on your list.
If there is no EMH night in a park, we select our nightly park by eliminating the park that had EMH morning and favoring a park that had EMH the prior day (and if that perfect pairing exists, we may take a chance and not go with fastpasses for the night).
The later EMH night starts, the less crowded it is.
The earlier EMH morning starts, the less crowded it is.
And who knows what the effect of Pandora is going to have on AK EMH - morning or night. At least the morning EMH in the summer is starting at 7:00, less early-birds at the gates.