Windows (~6 years) -> Mandriva (Mandrake? For I think 2-3 years) -> Ubuntu (1 day) -> Suse (2 days) -> Slackware (2-3 years) -> Gentoo unstable (2-3 years) -> Gentoo stable (2-3 years) -> Arch (9 years and counting)
The only span I’m sure about is the last one. When I started a job I decided I don’t have the time to compile the world anymore. But the values after Windows sum up to 21, should be 20, so it’s all more or less correct