What is love? Now that's a hard question to answer. Lately i've been thinking that the real answer to that is a special bond between two people. A bond so strong that it surpasses the physical (even though physical is pretty important to begin with). A bond that will make ordinary coincidences more and more often and will in time make you think "is this really a coincidence?".
First problem though, when it comes to love, is that most of the people confuse love with sexual tension/attraction. One needs a certain intelligence to grasp the concept and actually feel it.
Age isn't really important after a point, because if it was meant to happen then it was meant to happen, but it's generally better when there is a small to none age difference between the two.
Duration however is a whole different thing. Love as anything important is something very hard to attain. It takes time and effort to build a loving relationship between two people. You need to accept that person for what he or she is and, even though in time you'll try to change them, try not to change them too much.
In love, just like with everything else important to us, we always must be able to see beyond the present, and have at least a part of our mind set on the future. Because love is said to be eternal, right?
Answer to that is easy, it is! All you have to do is try, because if you want it, and i mean truly want it, then you will find it.