Firefox addons will now be only on WebExtensions

https://blog.mozilla.org/addons/2016/11/23/add-ons-in-2017/

By the end of 2017, and with the release of Firefox 57, we’ll move to WebExtensions exclusively, and will stop loading any other extension types on desktop. To help ensure any new extensions work beyond the end of 2017, AMO will stop accepting any new extensions for signing that are not WebExtensions in Firefox 53. Throughout the year we’ll expand the set of APIs available, add capabilities to Firefox that don’t yet exist in other browsers, and put more WebExtensions in front of users.

>>8
You don't need to maintain it much. If your userbase is a handful of neckbeards, you'll barely get any bugreports, and most of them will have patches submitted anyway. Firefox as it is works in 99% of cases, most of 'maintenance' will consist of doing nothing while the main Mozilla branch gets a pointless release every other day in a pointless attempt to imitate Chrome.