One reason for the 6 week update cadence that Firefox uses was to increase stability by reducing the pressure to include a feature in a release even if it's half baked. If not shipping at release time meant that the feature would be delayed for six months or a year while competing browsers pull ahead, there's a lot of pressure to just go ahead and release, even with known issues.

The approach, in my mind, has had mixed success, but has been a net positive overall. The biggest weakness is that it can be hard to maintain large architectural changes on a branch, which means there's still pressure to ship them in some form. (Though ideally with a configuration option to disable them by default.) Most things aren't like that, though, and for changes with a more controlled scope the six week cadence works very well.