Personally, I think one of the most important principles of effective teaching/presentation is repetition. Sadly, this is also the most forgotten principle. Presenters are in such a rush to pack more and more content into their presentation that they do not allow time for repetition. The net result is that they “cover” a lot of material, but very little actually percolates into the listeners’ minds. Most of the material simply remains in the Powerpoint slides or handouts.
My own style is to reduce the amount of content in my presentation to make room for repetition of key points through various means. I would much rather present ten key ideas/concepts and have seven of them sink into my listeners, than present twenty key concepts in the same time and have none of them sink in.
Ultimately, what matters is what the listeners take home with them in their minds, not how much the presenter has "covered".