Loading assets and page refreshes

Hi

I am thinking about the best way to design courses, and it may be dependent on the way SL loads.

For example, if SL only loads the assets page by page, is there any reason why a SL course shouldn't be quite large, say 100s of slides and multiple videos etc?

I'm assuming everything on layers is loaded at the same time as the slide, so that's a way to get instant response, but of course slows down the slide load.

Do scenes make any difference to the load behavior?

Is there anyway to preload or background load assets when a user is on a previous slide?