Hi Dan,
No it is not too late to let them court and breed, many boas will not start until later in the year (more true with True Red Tailed boas then Colombians)
However, Boa breeding is not like most Colubrid breedings, where you can breed them for a day or two and move him to the next girl. Male boas can take weeks to court a female until she will let him breed, so just because you saw activity and tail twisting does not mean a breeding took place. A older male boa (3 years or older) will have the ability to breed 2 females some have even reported up to four in a year, but the younger males normally will only breed one female per year. If you have noted heavy breeding activity with one female, I would not remove the male from her cage until they no longer show interest in each other for several days (this can take weeks) after that point you can try the next female, but many new breeders have struck out in a season by trying to mave a male around too much and end up with squat.
I hope this helps
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Jim Hopkins "Hoppy"
Hopkins Holesale Herps
Hopfam1@aol.com