You will get one update per year, and “only more often that that if there is a critical security fix”.

https://www.mozilla.org/en-US/firefox/all/desktop-esr/

Here you go brother. Hope this helps.

AFAIK there is no need to re-encode, since Youtube videos are stored and served in chunks anyways. The change is that they are now slipping in the ad chunks as if they were a part of the normal video chunk stream.