pretty much depends on the guy, and what you tend to do with him while you're with him
first of all
the guy type, some just get bored, some dont, I for instance can be with my girlfriend for hours and not feel bored. To some guy that would be like ?hell no?.
and on the second hand, what you do with him. First of all be inovative and imaginative. Usually the guy takes the lead in that, if you find that kind of a guy that is. Put a blindfold on his eyes and take him to your special place, make it romantic, but then show him some spirit and freshness in you and drag him to something wild and childish, like go on a rollercoaster with him. I am still not of your age, but I believe that if you find a guy, he will surely want to feel young again, if he feels young with you, you got a head start