I got this new '64 Legnano Roma, 56cm, as a sixteen year old junior racer. I'm 70 now, and the bike still fits like it was made for me. I put a slightly taller Nitto stem on it a few years ago, but its still one of my favorite and most comfortable rides. Unless you have some extreme growth or skeletal disorder, you might need to tweak the seat post or stem as you age, but that should be about it. Happy riding, and happy aging!
1964.
Same bike and rider at last year's Eroica ride.