Deliberate trolling gets you a 4 point infraction and lasts for 30 days.
Doing it again adds the same amount of points and extends the term by the same amount of days, i.e. you don't serve the sentences concurrently - you serve one after the other.
Should you break the point threshold of 10, you'll automatically be soft-banned (pilots license suspended) until you've worked off enough points to get you under 10 again.
So, trolling a bunch of times will extend the ban quite a bit, which may seem harsh, but then if you're mindful of that then you're unlikely to keep breaking the rules.
However, if you lose your temper and are abusive to other members by way of... say... posting a picture of them and insulting them, on top of all the other trolling that you did at the same time, you're likely to find yourself banned for a very loooong time indeed because that's just downright unacceptable behaviour and you should be taking a long hard look in the mirror.
There are other infractions that "extend" - these are;
Abuse of the thread tagging system - 2 points
Necro-posting - 3 points
Posting of a large image - 5 points
Insulted Other Member(s) - 5 points
Posting spam - 5 points
Posting a number of large images - 8 points
So, should yourself or another member find themselves banned for committing any of the above offences a number of times, well, now you know why and can be mindful that it was a self inflicted ban.