Anytime, and when feeding multiple smaller prey items (i.e. when I'm finishing off a bag of f/t feeders before moving up a size or something) then I tend to go for the 10% - 15% of the snake's weight. So pick two (or however many) rats whose weights add up to about 10 or 15% of the snake's body weight and it should be fine and give them maybe every 10 or so days (but you could wait longer if you fed a little bit over the 10-15% in that feeding)