They get tweeted based on when vBulletin sends me emails. If there's some frequency of posts on the forum or I don't visit often, I don't get the emails as frequently. It's not the most bulletproof system. I've been meaning to fix it, but with the NBA playoffs and all, I've been busy. I've got some time off work next week and may do something more precise then.
For those just looking to get the tweets, follow http://www.twitter.com/mad_capper and sign up for mobile updates if you want it to text message you whenever he posts. I won't (intentionally) post anything other than plays.