This is my experience aswell. When I was younger summer would last like an eternity. Now it's over in a blink. I think it might have to do with as we get older we take on more responsibilities(work, families, children, what have you?) and these keep us "away" from experiencing the now. When we were children we had less to worry about. Now there are always stuff to think about. My thoughts atleast.

In love...
/C