For normal adults, and both of mine are males, I feed them a large adult mouse every 7 days. The mouse is usually no bigger around than the snake. This is maintenance to keep them growing but not TOO much...especially my Ghost male.

1.5 times the girth is something I've never followed, preferring to give my corns a food item that leaves a slight bulge no matter what their age or size. The largest prey item I'll offer is no more than 0.5 times their girth. Others do things differently, but this works so far for me.