We used to do two week on-call rotations (to follow along with sprint/release cadence). At the beginning of '23, one of our devs asked to be full-time on-call, both because they had sleep issues and so would regularly be awake at 2 am, but also because they didn't like that the other team members wouldn't follow the documented processes.

They don't get paid extra, but they seem to be very happy with the setup.