My 12-16 lb breeder girls eat medium/lg (on the small side of lg, if that makes sense) rats every 10-14 days, depending on the snake & the rat. The "girth/lump" rule is pointless with bloods & STPs, as these snakes have very slow metabolisms & voracious feeding responses, and that combo can quickly lead to obesity.

Babies I'll feed good-sized (slightly noticeable bulge) meals every 7-10 days, but usually back them off by their first birthday or as necessary. Little ones will grow fairly quickly, big ones just get fat.