Ok I was not aware of that. Has it always been the case?
Since version 5 in 2011. For a while it was a monthly release, but since version 22/23 in June/August 2013 it's slowed down to every other month.
Well more or less, except the time was 1 year or more for "major" releases.
After Chrome went out and incremented major version with every release, firefox went after them.
Chrome doesn't have super huge list of new features either.
After chrome started a policy of version number inflation, firefox, firefox did the same for marketing reasons, else'd we'd be on like... version 6.6 instead of 66.0
No, it would be 5.10. Because, 1 to 4 are non-rapid releases, 5 would be the Servo epoch.