I think it will take about 5 years to get full size, that is if you give it the right light, fert, and water.
To answer your subject line, to maturity, about 50-100 years.

It really took off this summer after repotting, growing 25+ culms and still growing even as temperatures continue to drop. They're up to 4 mm thick and I repotted it in a ~3 trade gallon pot. Would that survive outdoors or should I bring it inside? I also have an unheated greenhouse but it gets moist and moldy inside.