Sometimes we need to prepare ourselves and encourage ourselves NOT to be the nasty self-interested exploiters that we could be. What could be worse for your YF than having you lose interest in him for no apparent reason? So you have some years to figure out how to find grace in ongoing supportive friendship. Or it may just happen naturally, but anyways, it's always good to scrutinize yourself and snip off a few budding outgrowths of selfishness.