im 20 and ive been with one bf when we were both 16/17 and that was kinda pants (but arnt all first times?!) hehe and then ive also been with a 23 year old whilst i was 19 (which was really good) and a 27 year old whilst i was 19 which wasnt quite the same!
Currently my bf is 19 (few months younger than me) and were always at it

so not really sure age matters i think it is just the sexual chemistry between two people. I did read somewhere tho that men reach there sexual peak at 19...no idea if this is right!