Linds,
I personally don't agree with keeping BRB's as cool as some people recommend. Yes can tolerate cooler ambient temps and no they don't generally bask at high temperatures but I would still suggest keeping their gradients moderate.
When BRB's are young I believe this is the time when to warm of temperatures could cause problems like dehydration and regurgitation. They should be kept very humid and slightly cool. IMO... 78-82 F works best.
Adult BRB's fare better at slightly warmer temperatures of 80-83 F with a basking spot of 86-88 F. I find that if adults are kept any cooler it seems to take to long to fully digest their food. BRB's do have a slightly slower metabolism (then average boa ssp.) but that's only by a few days depending on the size of the food item. Also like Grant pointed out, they grow much slower than you would expect. Most insular <i>Epicrates</i> grow very slow with the exception of the mainland forms and some larger insulars.
Insulars are another story when it comes to temperatures however but that's another long post. :0)
I hope this is useful to you. Best of luck.
Thanks,
Darren Hamill
http://www.hamillreptiles.com