I have never bred a female veiled until she was full grown (over a year of age). My reasoning has been that since ours are living in captivity why not make sure that they are done growing their own bones before we put the demand of laying FERTILE eggs on the?. I also don't breed and breed them....and as a result, most of my female veileds live to be 7 or older now.
I don't know what the disadvantages in nature would be for reproducing early...but in captivity, the calcium required to produce eggs is a concern to me.
Living in the wild, there are many differences in their lives from living in captivity as I'm sure you are aware, both in their favor and against them...predators, food availability, food quality and variety, stress, weather conditions that they have to endure (drought, heat, cold) just to name a few.
Just my 2 cents worth!