old friend, new spark

for some reason, i feel bad today... i went out on a date with an old friend.. a guy friend whom i've known since i was in college. He is younger than me, 3 years younger so that means I was already in college, he was still in high school. Well, let's just say we had a small thing then but we were both in college at that time... :) I was, i think on my last year - i spent 5 years in college and he was a 2nd year i believe.. anyway, he called me last week and I was surprised to find out he's here because last I've heard was that he was in New Jersey with his family. We then agreed to meet, he went to my apartment and we talked about a lot of things.. Well, he's older now and he has changed a little... he will always be the younger guy i kissed in college. it was fun to see him and reminisce our old antics. Boy, do i feel old. Well, that's life right.
From last week, we've been seeing each other, texting at least 100 messages a day... asking what each other is up to... To make it short, we were back to how we were 5 years ago. The difference is, i feel different, I like him - may it be that I don't have a relationship so I am considering a relationship even with a long time younger friend?? bummer, i don't want to think that I am desperate but i feel different.. i like him. and the sad thing is he's going back to the states next month. and the sweetest thing happened yesterday, we were cuddling and kissing when out of the blue i asked him if he remembers the first time we kissed, he told me when, where and how it happened, he even remembers it in a more detailed manner than i do. i was so surprised and i was just so flattered. i felt special. i think not even the guy i've been loving all these years with no reciprocation! and to no avail - remembers the first time we kissed, yet here he is... my good old friend telling me in detail our first sweet encounter... wow.. it felt good.
will i make the most out of our relationship while he's here? or do i bail out now to avoid getting hurt? we are not talking about relationships and i am happy with the set up but will i still be happy when he leaves? i also don't believe in long distance relationships - i have tried being in that type of relationship and it didn't even last 5 months...
will i be strong enough to keep my friendship with him even if i'm feeling different?
am i just desperate to be in a relationship that i am holding on to a friend?
when do i draw the line when the line is undefined... im confused...