> A slower release schedule doesn't mean you have more testing time. It means you tend to release more in one feature.
Plus, most of the serious bugs are found right away when a new group of users starts testing, e.g. when Firefox Nightly version moves to Beta or Beta moves to stable Release. Firefox Nightly, Beta, and Release channels have very different user populations. They have different hardware (Nightly users are power users with big, fast machines), software (Release users are more likely to use anti-virus software or not have the latest GPU driver updates installed), and browsing usage.
Mozilla's studies of crash rates and bug fixes for Firefox Beta showed that most of crashes and bugs are seen in the first two weeks or so. Having more beta "bake time" with a very long beta cycle has little benefit after the first batch of bugs are found and fixed.
An interesting historical tidbit: about 60% of Firefox Beta users are in India and Indonesia. That is definitely not representative of Nightly or Release user populations! The apocryphal story is that many years ago, a local computer retailer started passing around copies of a beta CD of Firefox 4 so people didn't have to download it over a slow or metered internet. And then all those people are still on the Firefox Beta channel.