I make most of my bets late because I like to see what others have said about the game before I bet. But I find a better selection of odds (greater variance) between 4 and 6 pm Eastern than between 6pm and 7pm (on weekdays when the games start at 7pm) because it seems the linesmen are on their toes during this hour whereas before that they don't seem to watch things as closely. Or at least that is my impression.
I like to bet into an early line, sometimes even overnight. Yeah, I get burned once in a while with suspensions or last minute injuries but I find I usually get good value betting early.
Usually early or late. Just depends on the game and how the line is moving. I have been helped tremendously by purchasing the premium Don Best line service. Highly Recommend!