I don't think porn will make you more likely to cheat, in the context we are talking about at least. I do think viewing porn can be a form of cheating because basically, you are supplementing your partner for other's visually in the moment you are mastubating to it and you might be taking those images with you into the bedroom and be thinking of the other people while your partner cluelessly thinks your thinking of them. But as far as going outside and physically sleeping with other's, I don't know.
I do think that people who are heavily into porn are not ever really ever satisifed with anything. hence the reason they turn to porn. So maybe that's the mentality behind thinking they are more likely to cheat. And probably the esculation of needing something to heighten the excitment.
5 times a day? What does he do? Just sit home all the time masturbating himself off? :/