I have to upgrade my Mint install every two years

I know you’re joking around here, but you don’t have to upgrade every two years. You can use an LTS release instead, or, on the opposite of the spectrum, a rolling release.

Release schedule and duration of support should always be factored into the decision of choosing a distro.

I’m not sure how they accomplish that

If they have database access, which they would have being the admins, they can do anything.