[microtonal]

Major versions of OpenBSD are only supported for 5-6 years.

I thought that security updates are only made for -current, the current stable release, and the previous stable release. So, 1 year of support, not 5-6.

A cursory look at the errata seems to confirm this.

[kijin]

Most of the time, upgrading from one minor version to the next is painless. If you installed OpenBSD 5.0, you are expected to keep updating all the way to 5.9. (For some reason, OpenBSD always makes exactly 9 minor versions for each major version.)

Most Linux distros don't even make any fuss about minor versions, using them only as an opportunity to build fresh installation images. New minor versions are security patches for the major version and all previous minor versions.