There are three main bans on ECC, the temp ban, normal ban, and the permaban. You can usually find the length of someone's ban by looking at their appeal here. /seen also shows Their "ban timer" if they successfully appealed or if they have a temp ban (usually short period of time).

The tempban is given for spamming before a restart for the most part. It will usually say "Ban Expires in: x days, x hours and x minutes" at the end of their /seen message.
The normal ban, which is what 99% of players receive is appeal-able here. I'm fairly certain that when the user appeals, they are given an automatic tempban, and their /seen will show the same message.
Permabans are a very special case, and only the worst of the worst get them. It's usually a 6+ month leave from the server, and sometimes there is no chance of appeal.

Just follow the rules and you won't ever have to worry. :D