There was nothing in his post that specified that he was immature. I hate to take sides but your first reply to his post was more immature than his post, I know its annoying answering questions sometimes but its pointless in writing "when you grow up". To answer your question love can happen at any stage and at any age, but yes maturity is required for real love. I have not been in love yet but I'm only 15 so I guess "when you grow up" is the only time it takes place. Even if it's fake love your feeling it's not a bad thing just don't propose and marry or do anything stupid(like decide to have a baby together, know it sounds stupid but it happens) and it'll be fine. Just don't get reliant on her. Thats the main difference between AFC love and true love.
Hope I helped,
Animal.