How long does love usually last? I've seen my friends parents and they don't look like their in love!?

I think I'm going to marry my high school sweetheart :D I'm a guy and I had a crush on this girl for 6 years, the first time I saw her, I was amazed by how pretty she was even until now. She started liking me 3 years ago and obsessively looks at me. I told my friend to give her a box of girl scout cookies and say it was from me and she told my friend to tell me thanks! And a lot of people say she likes me or I'm her boyfriend when we only know of each other but rarely talked to each other. I think she liked me for 3 years and I liked her for 6 years. I'm a senior in high school and for some strange reason, I'm still obsessed with her!? I'm no sucker... I'm just saying, I hate it when people respond to my question acting like I'm pathetic or I lack common sense, it's annoying. I know of a lot of girls that are interested in me, but for some reason.... I just don't care?!? Why am I so strange? One of the most gorgeous girls ever has a crush on me at school, she's my friend and for some reason.... I just don't care about her? She may even be prettier than the girl I'm obsessed with! A LOT OF GUYS LIKE HER!?!?! But I just don't care about her?.. and please don't act like I'm just a common thinker. I am the oddball at school and believe it or not... I have received the labels as a Prodigy,Psycho,Stud,Genius,Brilliant, Insane, Weird,Stuck Up, Asshole(been called this a lot.. even though I'm sweet inside, I only act out when my feeling of importance is insulted, WHICH IS A LOT).... The reason why I am explaining what I have been called is to get the idea that I'm no sucker... and I know it may seem egotistic, but typing these things about myself is a must for satisfying my contentment. I AM STILL OBSESSED WITH THE GIRL I HAD A CRUSH ON 6 YEARS AGO! Do you guys think I can spend the rest of my life with her being consistently happy year after year? =] I know for sure she likes me... and I know that you guys can only state your opinions because no one can really tell me the outcome of my life. I want to spend my entire life catering to her!!!.. Am I just being crazy? Am I just in love of the thought of being with her? I don't really know what to believe anymore.... I've ignored so many girls for this one!?! Am I just being stubborn overestimating this girl thinking she is the one?