I use Nightly exclusively. Unless you are somehow installing Nightly updates in a way that the binary is owned by a user who isn't you (ie, owned by root), Nightly will never force you to restart, it just forever has the green dot on the hamburger menu.
This is true for me on both Windows (and my user is part of the Administrator group, thus can write to a global c:\Program Files install) and Linux (and Firefox is installed to a directory in $HOME to simplify the process of non-packaged binary management).
Now, I also have Firefox (stable) installed as a .deb (to fulfill the browser dep). If the .deb gets upgraded by apt, that Firefox suddenly bricks itself until I restart. And this is intentional, btw, given how Firefox interacts with itself to do process isolation.
Everything I say here has been true for roughly the past decade.