Permanent bans are given out in extreme situations. It's always up the administrator giving out the ban, however the ethos is used as a guideline for staff and bans go by this guideline. You won't get a permanent ban just because you have a recent ban. Extreme situations can be stealing server files, hacking (second offense), or by having multiple recent bans and constantly breaking rules. It's always up to the administrator though, doesn't meant the ban is right though that's subjective depending on the length, reason, and situation.