How Long Does Hairline Maturation Take?

In your experience, how long does the maturation of the hairline process take? I just recently noticed a slight recession on the corners and I was just wondering.

The maturing hairline is an insidious process and can take years to appear. The process is very slow and creeps up on most men. I watched two of my sons and my nephew gain mature hairlines, and each took a number of years to fully appear.