A couple of questions

As with anything you will see good and bad outcomes from a number of situations.
I am using experiences with a number of other herps to base my breedings being over 2 years old more to the three year old mark for mine.
I too have heard mixed stories on the 18 month issue but "Just my opinion here" I believe 18 months is the earliest they are able to physically able in general to breed, I have decided to wait a year or two more out of experience with other animals producing healthier, stronger young at an older age and having less complications them selves sue to stress.
I know there is a huge difference between chameleons and boas but as an example, Chameleons can be bred early and with proper cycling of light and temps up to 3 times a year. Back then average life expectancy was 3 years rarely more. I bred mine once a year at 1st then twice a year later on. I find the males bred more frequently had shorter life spans and were more prone to illness.
My prized male bred only 2 times the 1st time he was almost 2 years old, he lived to be 7 years old.
I know that I have a lot to learn with boas but hope that some of these practices help with this endevor as it has in the past with others.
I know this is inconclusive and only my experience with chameleons but I find it applys in theory to all herps