I am wondering if there should be a comma before the word "except" in this sentence. The research I have done reveals that commas usually aren't used, but I think that it depends on the sentence. I cannot find a significant explanation as to when commas would be used or not. My instinct is that this situation would be the same as a comma before "because:" add a comma if necessary to avoid confusion. Is the sentence below correct?
"I have been the judge of hundreds of card tournaments, and I do not have any disciplinary actions on my record, except for two warnings that were given years ago."