The gouda that I am making will age for 18 months before I "try" it. The gouda at the store that is crumbly is between 18-26 months aged.
The Beemster XO (extra old) is at least 26 months.
Also, the natural rind is washed with brine every other day for about 2 months, and not waxed from what I know. (I am not putting wax on mine)
The Salt brine will dry out the surface and create a natural rind. This should also draw moisture out.
I am truly no expert here, and this just about encompassed all i know of gouda.
I will let you know how mine comes along.
SalMac makes more gouda than anyone i know. He might have more meaningful insight here.