In a day???? None, most of the time. I generally watch a movie every two or three months. Some months, maybe as many as two, but that's an unusual month for me. One is all I'll watch at any one time. One good movie is enough for me for a good while, and a mediocre or bad one is all the "boring-and/or-draining" I ever want within any brief time period.
Having said that, I can't really say I think there's a "too much" for some people under some circumstances. If someone is a grown up (and out of school and is old enough to be past the stage when the brain is still finishing up with development), isn't working, is on vacation, or otherwise doesn't have a whole lot to do (or any number of other situations/circumstances); and if there's some reason he enjoys watching movies all day, I'm not sure there's "an official" "too much". It's not the most well rounded thing to do in the world, but sometimes life circumstances mean that a person goes with what he finds enjoyable for the time. If somebody's in a situation where he kills off an evening by watching three movies in a row, I'm not sure there's anything all that wrong with it (especially if his mornings, days, dinner times and nights include more balance). Or, the person who chooses to have a marathon movie-watching day here and there isn't necessarily lacking balance in his life either.
Achieving balance in one's days is best. Aiming for balance is good. Having to live with less than ideal balance is something people in some circumstances have to do; and if someone gets enjoyment from watching a string of movies in one sitting that can be more balanced than being bored or unhappy.