We waited till our older son was 11 months before letting him watch Hi-5, Brainy Baby and Baby Can Read. We then introduced at 18 months, other content such as Blues Clues, Kipper, Wallace and Gromit, Pre-School Power and VeggieTales. Disney, including Little Einsteins was only introduced at age 3. We found that he was very sensitive and would get "stressed" watching anything with any tension in it. We also favored the ones where the narrator/characters spoke clearly and where the film editing didn't frequently cut in and out too quickly as some children find it dizzying. We averaged about 2 hours a day when he was younger, but we probably watch no more than an hour a day, now that he has more things to do. He was speaking and reading by age 2 and I do credit the videos for introducing new ideas to him - at least more than my energy and level of creativity would have enabled at the time as I was working full-time then. Of course, our younger son was watching anything his older brother was watching, so he started earlier. He's not yet 2, but is speaking earlier, but not yet reading as I suspect we're not quite as organized in how we've been introducing new things to him, so he's probably more confused!
The other thing was that our children loved to listen and dance to music. We'd have music in the background about another 2 hours a day. I would also separately have DVDs of what the adults wanted to watch - generally, orchestral performances, which the children would also enjoy a couple of times a week.
