Please add something like browser.privatebrowsing.forceMediaMemoryCache for normal browsing (non-private).

Video caching to disk adds gigabytes of needless wear every day to SSDs and live USB sticks, and modern computers have large RAM storage anyway.

This is the same reason Mozilla chose to compress json sessionstore backups. (But video is already compressed so it can not be compressed any further with lz4 or gzip.)