My husband insists that men can only physically go on with no sex (or masturbation) for a maximum of 3 days. Is this true?

Not true! A man's sexual desire is actually linked to his testosterone levels - which can also be tested medically. An average man would have a level of 3-5, while those who have "bigger sex drive" will have higher! These are actually hormones in play, one of the ways men can control it is with exercise (using adrenaline and other hormones produced during exercise to balance it).