A slow grown boa is the best boa. Usually reaching adult size and maturity around 5-6 years (imo).
May seem small for the age to some but boas will reach their full potential.
I forgot to address the feeding schedule - I'd go every 2-3 weeks or so for a young boa. Once they get closer to 5' or I consider adult, I move them out to 4-6 weeks.