Actually, most people on dsl or cable have their IP's change with surprising regularity. I have had cable and DSL for several years and even when I pay extra to have a static IP, my IP changes more often then I want!
However, his IP will be probably be banned long enough for him to contemplate creating a new account, make an attempt and be denied.
If he was then really savvy, he might try a proxy or somesuch, but from the sounds of his posts, he lacked technical skills to pull something like that off.
Regardless, I am sure the banning served it's purpose...