If a man gets the strap-on frequently, over time his body and brain will adjust to his new circumstance, and all kinds of changes, both physical and psychological, will happen.
His sexual pleasure zone, for example, will slowly start to shift from the head of his penis to his asshole. This change will be accelerated if his penis is locked up 24/7, and the only time he’s allowed to cum is when he’s fucked in the ass. His body and brain will eventually start to associate anal penetration with orgasm.
Over time he will begin to not only enjoy it, he will start to crave it. Such that if you withhold the strap-on for a while, and don’t let him cum, he will miss it, become extremely anxious about it, and will eventually ask you for it. That’s when you know that all your patience training efforts with him have paid off