This subject is long and involved and there are various ages/stages in the snake's life that require different feeding intervals.
THE COMPLETE BOA CONSTRICTOR by Vincent Russo has very good information on feeding.
My copy arrived two days ago but i cant open it until father's day!
1.0 Central American BI: Irwin
0.1 Jungle, het snow BI: Gimel
1.0 green albino, het granite Burm: Dr. Waffles
1.0 Betta fish: Convertible
1.1 cats: Tipitina (Tipi) and Professor Longhair (Fess)
0.1 Egyptian baladi dog: Toasty