There really isn't anything in the rules which explains how long a BAN lasts, and in some (most?) cases, it should not be called a BAN as some ****** members have been allowed back on the board. It would be better to call it SUSPENDED. I say this because last month, I saw one user who was ****** (suspended) on 3 different occasions for extreme flaming, but he is now actively posting again. ****** should mean ****** as in never again allowed back on the board, but that's just my opinion.
Actually, when you go read the rules thread there is a link which explains what infractions are and it also shows the different ban periods and infraction points connected to it.
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the link in case you can't find it
The Banned4Life is actually an additional usergroup. For those of us (Raymond and I) who deal with the back end of the board and all the tools, it's a real pain to have 2 usergroups for ****** people. So we just stopped using it. ;-) Makes management much easier.