If you don't like the 2 year release cycle, use Ubuntu, which is Debian-based. Debian maintains such long release cycles because the tolerance for bugs and incompatibilities are smaller than other linux distros. For long-lived applications or applications that have long planning periods Debian is ideal. NASA uses Debian, because their projects are measured in years, have low tolerances for bugs, and are developed to last 5+ years. Simply put, Debian's release model is for a different use-case than your typical web development project
It's really very nice to just throw Ubuntu 14.04 on everything and not worry about it. I can use my machines for doing work and not have to waste a lot of time dealing with whatever the latest churn is.
Ubuntu releases come every 6 months with a LTS every 2 years.
The non-LTS releases are of pretty questionable quality and are only supported for 9 months, which makes them pretty awful for server use.
Debian releases and Ubuntu LTS releases are about equal. New releases come every ~2 years and with Debian's new LTS policy, both are supported for 5 years in total. So you could say for server usage they have similar release cycles.
User experience stability is often a real problem in the corporate or institutional world. Keeping a maximally stable version of Firefox will help corporate users a lot - it's not even necessarily about stability as much as it's about user retraining, in-house extensions, etc.
For most companies what version of firefox probably doesn't matter. However, there are tons of legacy desktop apps in government, call centers etc where installing a new version of firefox will break the application. Hell, the callcenter my company uses an app that will only work with certain versions of ie. The company that made the app went out of business years ago and the only thing the call center has is a binary they install on all desktops.
