My beard was a lot thinner when I was 22 than when I was 30. Back when I was 22, I could shave and cover with a simple powder foundation and the cover would last at least 12 hours; by the time I was 30, I had to use heavy creme foundation to cover and the cover only lasted 4 hours or so.
Your beard gets thicker as you age; different parts get thicker at different rates. Has nothing to do with whether you shave or not.