Here's my take on emh.
Whether to go or not to go to emh really depends upon your situation. I do have a few general notes. None of these are hard and fast rules except possibly number 1. There are always exceptions. But these rules seem to work in general. .
1. If you are staying offsite, avoid emh parks. You cannot go to the emh and the extra crowds at an emh park will cost you time.
2. If you do not have hoppers, avoid emh parks. You will likely give back the time saved at an emh back during the rest of the day with extra crowds. An exception might be this. If you go to a water park for the day, you might just want to spend that evening at an emh park.
3. The consideration of emh is dependent upon the crowd levels in general. . During slack periods, the extra crowds an emh brings in aren't likely to matter much. So you'd cerainly want to consider emh. Additionally, when it's totally packed across the board at WDW anyway, you might want to go to emh. It still brings extra crowds but much like 105 and 120 are both miserably hot, it's going to be miserably crowded anyway and the extra hour(s) might help.
Morning emh.
4. If you have hoppers and you plan to rest during the day, go to the morning emh park until about lunch time when it really fills up, then hit the hotel. Then head out that evening somewhere else. This is where emh is most effective in my opinion.
5. If you have hoppers and plan to hop directly to another park after morning emh, know that you'll be giving back about 1/2 an hour to transportation. You will also be behind that initial push at the hopped to park if you leave right after emh and if you leave later, you will miss prime morning touring at the hopped to park entirely.
Evening emh
6. The later the emh, the less crowded it will likely be. For example, an 8-11 emh at the MK will likely be crowded. A 12am-3am will be sparse at 3am. Of course the downshot is that it's less likely you'll want to get up the next morning for early touring.
7. These are in general more crowded than morning emh but they are 3 hours instead of 1.
Almost forgot two last notes
8. If Disney adds an emh while you are down there or just before you go, avoid that park. They've just received data that indicates it's going to be jambed. Avoid it if you can. Two trips ago, we couldn't, and we paid the price. We still got things done in the morning, but the rest of the day it was Wall to wall in FL
9. If there's an emh for the MK the whole week, go on your normal day.
So you see it really depends upon your situation what you would want to do and note that there are always trade offs.
As for us, we do not get hoppers. We stay onsite. We do the water fun and more package. We go during a time that is not insanely busy nor slack. The kids simply will not nap. So they'd be all, can we go yet, can we go yet. Given the above, we avoid emh unless it just so happens there's an evening emh we want to hit on a water park day.
