Carolyn Hax: How long should you date someone who’s only ‘good on paper’?

Dear Carolyn: I’m in my early 20s and starting to date with more intention. How long should I keep going on dates with someone who is super good on paper but I feel lukewarm about? I understand first-date jitters, and that things can often improve on a second or third date, but I don’t feel super excited or like I have a crush. Do those giddy, exciting feelings fade as you get older? Wondering if comparing adult relationships to my teenage romances is unfair.