Text is cheaper than video

Text materials are generally superior to video because they:

are faster to create and edit
uses less disk space and network bandwidth
is easier to search: Ctrl + F on the browser and off you go. And then grep if you have superpowers.

Only produce video material if:

it shows an experiment, physical technique, natural phenomena or location that is of interest. See also: Section "Videos of all key physics experiments"
it gives fundamental geometric insight on the subject
you are filming a human transmitting their passion about the subject, and the speaker is amazing, and does not speak for too long

Never create videos of people just speaking hardcore content for long amounts of time.

If you have to use videos, make them as short as possible, and index them with a textual table of contents.

Also consider using sequences of images or GIFs instead of videos, since those are cheaper.