If you were given 20 points for an Infraction, you would be banned permanently.

However, if you were unbanned afterwards the points would remain there until a moderator decided it was time to remove them.

Usually, S-Mods and higher use different moderator tools to ban people permanently so you may not even receive points. However, in the case of other staff like GM's, you would receive the points until someone removed them or reversed the Infraction.

Just because you have 20 points, doesn't mean you'll be banned forever.