Jail is an issue only to aging mortals. It’s a FOMO maximiser: having to spend X% of life under stern conditions means losing a meaningful part of the limited time available to live.

If humans didn’t age and die, any jail time would tend to zero as a percentage of life spent. It would no longer be an issue.

Practical deathlessness will lead to rethinking the punishments given for crimes. Murder would become an even more serious crime, as folk would be dying very seldomly.