I have something like HFM so LO (3.5yo) is watching a lot of TV. I think she's on hour 2 or 3. I'm pretty sure she could watch for 6 or 7 hours if I let her. She's never fallen asleep in front of the TV or left it voluntarily. Once I turned the TV on in the middle of the night when she had bronchitis and needed breathing treatments. After trying to get her down I fell back asleep on the couch but she was still transfixed when I woke up at 3am. MIL always tried to get LO to fall asleep to a movie but it has never worked. We don't usually watch much TV because LO is obsessed so while she's like to consume tons she doesn't get to.