sex isn't everything in a relationship. Remember that. You both will be growing old and other things other than sex are more important. So I wouldn't end it with her b/c of that. Your hormones do settle down though when u get older. I don't think you should be pushing for sex, coz she'll just push you away.
As for the vacation thing, personally if I was staying at someone's home I'd feel uncomfortable having sex. It's just for respect. You can look at it in a different angle that it's a time to spend and relax with someone you love ( you don't have to expect sex).
heh just try to control yourself, as cardinal said. Take control of your body, don't let your body control you.