[DonGateley]

As could be expected this has poked a hornets nest of opposition because of its implications regarding backward compatibility of extensions we use. Many of us are hoping for a fork based on the current release that will continue to evolve and be maintained and which values backward compatibility first and foremost.

Users can snapshot the current 40.0 release by copying the installation directory and creating a cloned profile for it with updates disabled. Personally I find the 42.0a2 development channel release to be backwards compatible with all extensions and to have superior memory management.

[geofft]

Are you hoping for a fork more than you're hoping for all your extensions to be ported (or reimplemented by different people) on the new model? I bet this is super frustrating for established extension authors, but as a user, I bet there are enough users that the demand will be there for all the common extensions.

Anyway, if you're staying on an old release, please use Firefox 38 ESR (or switch to the ESR at Firefox 45, on the assumption that this change won't be complete by March). Sticking with Firefox 40 and disabling security updates seems like a terrible terrible idea.

https://www.mozilla.org/en-US/firefox/organizations/faq/