Exactly. When I was 15 I used to think that 25 was 'getting old and mature'. Now that I am about to turn 25 in November I just realized - oh shit Im only five years from 30! Not that 30 is old, but around then you start losing your physical youthfulness. I say if you have the chance love and live your life in your 20s.
Besides age is just a number, maturity is something you never fully complete - as you age you get more mature. In other words you never stop growing.