Mozilla has announced the Firefox Extended Support Release. More information will be coming out soon, but what I can find basically states that instead of a rolling, 6-week release schedule of the mainline Firefox release, the ESR version will be once a year and then security and critical updates will come out during the whole of that year for that version.
Starting with Firefox 10 (which will be the first ESR release), every year there will be another ESR release that will follow the same version number as the Firefox that is being released then (for now, that would mean Firefox 17 in 2013 and Firefox 24 in 2014). Then x.0.x releases would come out during the whole of the year for security issues, mainly coinciding with rolling in the security fixes of each new Firefox release: Firefox ESR 10.0.1 would include the fixes from Firefox 11, Firefox ESR 10.0.2 from Firefox 12, 10.0.3 from 13 … you get the idea.
This will not be advertised through the Mozilla site but available through their Enterprise wiki page. You can read the draft of the proposal at their wiki as well.
This is great news and I think a good compromise for businesses and other organizations instead of needing to work around the rapid release of the mainline Firefox.