The question is one of control- do you indulge to the harm of things you
consider more important, and do you do so because you feel compelled to do so by uncontrollable cravings. If yes, then the periodicity is basically irrelevant. You could be addicted to a drug that the cravings only come every 4 months and be able to put up a great appearance- but when the cravings hit you'd sell your first-born for- I'd say you're addicted.
There are plenty of people who've been fired from jobs because they couldn't restrict they porn-consuming behavior to personal times, places and devices. I'd say those who risked that for something they could get in a couple hours anyway are addicted.