That'll be hard. There was research a few years ago trying to determine something-or-other (I can't remember what it was) involving men who used porn and those who did not.
They had to abandon the study because they could not find one single male who would admit to satisfying the latter criterion. Now, admittedly, this being a psych study the sample set probably consisted entirely of psych undergrads, who are young and thus suffering from a degree of testosterone poisoning... but fundamentally we are visually activated animals and it appears likely that pornography is eternal. (Some of the first recorded cave art, those 'fertility icons'? Plainly prehistoric porn. The stuff is probably older than Homo sapiens. Good luck stamping it out.)
(Some men may go off it later in life, but I suspect that marriage and/or declining testosterone levels are more to blame than anything else.)