Mature Uromastyx
There are at least 18 species of Uromastyx.
See the
Reptilles Database for descriptions and pictures of the 18 species of Uromastyx .
Uromastyx mature in like 3-5 years depending on care and environment. At around 3 years or so they become old enough to breed and reproduce. All my U.ornate females that have produced eggs for me so far have weighed at least 200 grams. My Ocellata was only 120 grams and she laid eggs. So it depends on the species you are working with when it will be mature and ready for breeding.
Audrey Vanderlinden actually bread 1 yr. old U.ornates.
See the
UROMASTYX HOME PAGE -The Captive breeding update on Ornate Spiny Tailed Lizards.

Above picture is a 4 year old mature U.ornate.
Uromastyx are a long lived species and have been reported reaching 10+ years in captivity. I believe with proper diet
and care they can far exceed this, maybe even go to the 20+ years old range.