You can't get fat in a day!
I have one cheat afternoon a week where i usually eat a shitload of food.
However i've seen me taking a sat/sun/mon off the gym and the diet if im not feeling it. I'm confident i would never go back to my old ways so don't see it as too big a problem, obviously not something i'd be doing every week but every 4/5/6 weeks, i don't think is too bad