"I've heard that the younger a man is when he has the procedure the more likely this is to happen. Anyone know if this is fact?"
Logically, this is true. If the man and woman are about the same age and, say, he gets a vas at age 35, if it fails after 10 years, his wife will be 45 and her chances of getting pregnant will be pretty darn low. OTOH, if he were to get a vas at 25, she will still be quite fertile at 35. In the first case, he will never know his vas failed as he will never have a reason to get tested. In the second case, he will certainly know.