To clear things out, here's the different ban durations:

Points --- Ban Period
8 ------- 3 Day(s)
9 ------- 7 Day(s)
10 ------ 2 Week(s)
11 ------ 1 Month(s)
12 ------ 3 Month(s)
13 ------ 6 Month(s)
15 ------ Forever

A ban does not necessarily mean a lifetime ban of that particular account.
As listed above, a ban can expire after 3 days, a month or forever.

If a certain person was labeled as "banned" and then he/she came back after a week, it does not mean that we allowed him/her to come back, or special treatment, or amnesty. The ban just simply expired.