I have had two females from my 2001 litter gave birth to small litters in 2004. That equates to breeding at 2.5 years old. I don't feel I am "power feeding" them at all. My basic regimens:
Hatchling, first feeder (if available) is a hopper mouse. Either a few days after birth for those full term, no yolk babies or after first shed for the younger, still have yolk to process babies.
Neonates. Fed weekly, typically on Monday, if they refuse, they don't get another chance till the following week. Typical refusal tied to shedding and many will still eat even when fully opaque. Food size based on baby size, as they grow, they get bigger meals, always about the size of their thickest diameter.
Yearlings, get switched to every other week, same basic releative prey size. Sometimes I don't have the "right" size and feed two smaller. I base the feeding on tummy size, one appropriate sized feeder makes a certain sized bulge, two smaller make the same bulge.
Adults, get's trickey, as you know they mostly refuse food while gravid/breeding, Then make up for it after giving birth. So....
Males - fed two to four week intervals depending on time of year.
Females - offered small prey monthly while gravid, then fed every two weeks (sometimes weekly) after partuturition and before the next breeding season. Realistically only 5 or 6 months.
Also, for all, I raise my own feeders and sometimes feeders are scarce, I have been know to have a fast week for all the snakes to allow the feeder colony to catch up. In addition, We typically take two week long vacations and another 5 day vacation yearly. For those times, I stop feeding a week and a half before leaving so the snakes will have time to purge their waste before we leave and not mess up the cages/water bowls while we are gone, bottom line they have two and a half week fasts three times a year.
I have 2.5 two year olds, most are doing quite nicely towards being of breeding size by this fall. The following weights were taken on 04/20.
The males:
Rusty, 1-lb, 1-oz - my smallest two year old, he's a finicky eater and will probably not breed this fall
C1, 1-lb, 15-oz - well on the way for fall breeding
The females:
Daisey, 2-lbs, 6-oz - One of the biggest girls and also the best looking of the group...duh, on the fall breeding list
S2, 1-lb, 11-oz - borderline, will have to see how the summer goes
W1, 2-lbs, 8-oz - My largest girl, on the fall breeding list.
W2, 1-lb, 10-oz - another borderline.
C2, 1-lb, 12-oz - Another borderline.
All three borderlines are looking good and still eating well. They may very well be ready for this fall.
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Thanks,
Dave "Rainbows-R-Us"
0.1 Wife (WC)
0.2 kids (CBB)
2.7 Brazilian Rainbow Boa (adult breeders)
2.5 Brazilian Rainbow Boa (sub-adult from 2004)
4.8 Brazilian Rainbow Boa (sub-adult from 2005)
2.1 Hypomelanistic BRB
0.1 Het for Hypomelanistic BRB
0.1 BCI "Elvira" normal from 1989
1.0 BCI Albino / het-anery
0.1 BCI Salmon / het-albino
0.1 BCI Anery / het-albino
0.1 BCI Salmon (possible super)
1.0 BCI Albino het stripe
1.0 BCI Salmon
0.1 BCI Ghost
0.1 BCI Super salmon, possible jungle
1.0 BCI Salmon, possible jungle
0.1 BCI Super Ghost
lots.lots.lots feeder mice and rats 
