My old school did 2 hours. That was back in the early 80s. The first 20 or 25 minutes was warmups, followed by another 20 or 30 minutes of basic blocks, punches and kicks. After that was forms, and in this case, the lower belts got a mini break as they only had to do the basic forms, then sit and watch the higher belts do their forms. Then sparring for about 15 minutes or so, or sometimes self defense techniques. My current school does 1 hour classes. First, while they do a warmup, it is more of the dynamic variety than the multiple static stretches my former school did. So I realized I need to arrive early and spend some extra time loosening up. Now, I haven't done any sparring yet and it looks like my current school does sparring only classes and doesn't do sparring at all in most regular classes. It is a different way of teaching, but I see the benefit. Though I haven't done a sparring class, I have watched them. I think it would be easier to maintain or even learn slowly going just once a week at my former school than at my current school. Given the shorter duration of the classes, it is incumbent on the student to go more often, or at least do some practicing at home. I saw an example of this last week. A woman who had just been awarded her green belt just a few weeks earlier showed up in class last week. I get the impression she doesn't train very much. She struggled to remember the yellow belt form. And she struggled with basic kick combinations, like front kick, roundhouse, or side kick hook kick. The assistant instructor had to pull her out of class and break down the basics of throwing a side kick and a roundhouse.