I am using 14 different extensions in Firefox. I don't think any of them have broken due to a Firefox update for at least the past 3 years.

The only maintenance I have had to do was when the "I don't care about cookie's" extension got sold out, so had to switch to a fork [1]. That was 2-3 years ago.

[1] https://github.com/OhMyGuus/I-Still-Dont-Care-About-Cookies