ugh the pet store here has a somewhat local breeder, who so far has bred the defective blue gene that's killed mine and my coworker's fish -.- That breeder doesn't get Thailand fish... if they do they are not helping with genetics!
I got Spartan at I think 6 months... he was an inch. Now he is 2.5 :) Any other betta since then other than the girls have all been about 9-11 months... Females probably 3-5 months. But I've noticed quality of bettas here taking a nose dive!
I've adopted out 5 of my bettas. And each went with a brochure, talking about feeding, cleaning, temperature, tips and tricks, etc. No pet store here does that ;)
Breed for the breed, not for the money; the words any REAL breeder would understand.
You must know nothing in order to know all, for all is nothing and nothing is for all.