i have "Check for updates but let you choose to install them" set but firefox still installs updates against my will without my choosing to install them
What OS? That preference works on Windows, assuming you are not drastically out of date, but on Linux, the package manager doesn't necessarily pay attention to settings internal to Firefox.
Hmm, I wonder what is different on yours. That has worked for me since version 1. That said, I usually update within a week. How long are you trying to snooze the update?
It definitely does not work indefinitely. If I recall correctly, several years ago a failsafe was added where very obsolete versions were assumed to have update check failure and were forcibly updated. Or something like that.
If you want a version that has fewer major updates and bug fixes, you could look at the Extended Support Release. The ESR based on Firefox 91 is nearing its "end of life" and will be moved to an ESR based on Firefox 102 in the next couple of months:
