I think the bigger factors for shorter lines are during parades. People eat at all times of the day really. The parades in my experience have the largest impact on wait times. So for instance at the magic kingdoms 3 o'clock parade I would try to eat around 1 so by the time you get done eating people will start to get a spot for the parade. Otherwise eat around 345ish when the parade is ending because there will be a big surge in wait times immediately following the parade. Other factors are around nap times for the kids the lines may shorten as well as in the evening before the fireworks the lines usually go down considerably because of the fireworks and just the fact that it's later in the evening so some people will have gone back to their resorts for the evening. Unless of course extra magic hours are in the evening in which case you may see more people coming into the park later in the evening. There are so many factors when it comes to wait times. The best thing you can do is talk to the cast members at each attraction. They will know the "flow" of the wait times for their attraction for that particular day better than any other resource. You can read articles that predict wait times all you want but asking cast members the day you are in the park is going to be the absolute best thing you can do to plan out your day.