To think of forever, or the rest of your life, or until you are old and grey, is a very long time into the future for being only 16.
Forever is a very long time for any age for that matter.
But what you might be missing betwteen the quick decision of whether or not this person is forever, is all the good stuff in the middle.
By judging a potential boyfriend too quickly, you could be missing out on developing a friendship, and that is always where any relationship starts. Maybe try thinking friend first, and allow enough time to get to know a person. Forever never has to come, and probably shouldn't come until you are at least in your 20's.
And how do you know? It comes with maturity, and experience, and not denying yourself the opportunity to date lots of guys; that way you learn what relationships are all about.
Being hurt, or trying to avoid being hurt, isn't realistic. Better to be hurt over a friendship or relationship that doesn't work out, now, than to put all your hopes and dreams on one forever relationship, and learn not only you were wrong about that person, but that you also missed a lot. You will be hurt, and confused, and go through all the emotions that being hurt entails. The bright side is, we all survive that maturing and growing, and go on to make better choices.
Try to think more of enjoying your life, your friends, your activities, etc., and less of a forever boyfriend. Friendships will last longer, and be more meaningful now, than a boyfriend.