I have a Saharan (common U.Gery, but also Niger species). My Sahahran SHed until he was a full adult, about 15"-17" depending on the critter. Generally, I have seen that the Mali female I have is actually longer than my Male Saharan, if that helps.
I bought him as a wild caught, and there was not much I could do to help him shed, he just underwent the process from around Nov-Apr (Northeast USA) andsuddenly this last fall stopped. I remember him being really nasty during his last shed, and hoping it would be his last. I never got his age, I just knew that he was imported in 99, and went to a 7 year ols, who totally freaked him out by chasing him, and then I adopted him as the pet shop really didn't want him there. In any case, it is quite normal for them to shed until adulthood, so if you have another that does not shed, you are right, he is an adult, and it is possible depending on size (these guys seem to age really slowly, then like Sleeping Beauty"pow"0) that this Uro could end shedding at some point. I would say around 15", give or take 1"-2", as I am not so set on the standard as most are. You are lucky, you have this forum, when I got mine I was lucky to get an article on their lifestyle in Reptile Magazine, and it wasn't all correct. Please be careful with what you learn.
Lisa