if this is authoritative
https://bitcointalk.org/myips.php I would say that the IP address is remembered only for 30 days. at least that's how I see it for my account.
Thank you. I was looking for the link to find the correct retain time. I was in a doubt if that was for 3 months or 6 months. That's why I did not put a time there.
I'm very curious, about what kind of trouble connecting an IP address with an account on the forum can cause?
Finding location could be a good reason. Many users do not use vpn/tor. With the IP addresses you will at-least know their location.