The length is really dependent on the lesson topic being presented. But Aeromedical Factors is one of the longer ones. Off the top of my head, I think mine was 7 or 8 pages. How you format it is another thing. I've noticed a large chunk of people that use full sentences for the whole thing, while others stay true to an outline of key points and phrases. If I used full sentences, I'd be spending too much time looking at the paper.
Premade lessons won't always have everything that you need on there for yourself. The converse is also true, they may have too much info that you don't need there. I wouldn't worry about the length too much. Include whatever you need to include to adequately teach the lesson.