Unlike other fast growing lizards, uromastyx grow relatively slowly. Mine took about 6 years to reach his adult size of 18" tol. But during those 6 years, he grew in spurts and at times didn't grow much at all for several months at a time. It seems like he had his greatest growth spurts in late spring. As I recall, when he turned about 8 years old, he had a big growth spurt. btw, looks to be aegyptica aegyptica, but given the occelations on his back, he could be microlepis. Either way, he's going to be a big fella.