To me it sounds a bit unusual for a person. I associate the expression more with historical periods or periods marked by technological advances.
eg. The golden age of the steam engine.
The golden age of the Roman Empire.
The golden age of psychological analysis.
So it seems to imply that it is finished and part of the past.
For a person in their 20's 30's the most usual expression that comes to mind is 'in the prime of (his) life'.