What do you mean by 'compatibility-busting'? New Firefox releases (and, I assume, Chrome and Chromium) have pretty good compatibility with everything except old plugins. A new release may add features, but the web being what it is, it's rare for browsers to break compatibility with existing sites or web applications.
That is why most distributions, including the commercial ones with long support windows, are happy to package the latest browser versions as they come out. Keeping your users on the same four-year-old browser (with only security fixes backported) is not long-term support worthy of the name.