It works well on the latest version of Firefox.

I've been looking for one for mobile, and found yours thanks man.

I have also added the "YouTube uninterrupted" at the same time as "play YouTube in background" from this same developer group. I cannot tell if it is doing it's job or not. However have using for a couple of hours without any issues/pauses--which is exactly what it should be doing! So I believe both extensions are a win.