"You meet more native 16s at the Worldwound than native 15s or native 17s, and that's typically fifth circle casters or higher. The average age to third circle is ten years, and it's known to be faster, but not lots faster - maybe six or eight years - if you're smarter, though also very smart people sometimes get stuck and obviously this is conditional on you being at the Worldwound and using magic where it matters. 

The youngest fourth-circle caster in Cheliax is a native 18."

"You meet more native 16s at the Worldwound than native 15s or native 17s, and that's typically fifth circle casters or higher. The average age to third circle is ten years, and it's known to be faster, but not lots faster - maybe six or eight years - if you're smarter, though also very smart people sometimes get stuck and obviously this is conditional on you being at the Worldwound and using magic where it matters. 

The youngest fourth-circle wizard in Cheliax is a native 18."