 Six psychological facts you might not know about best friends. We typically have about two best friends. We devote about 20% of our available social time to these two friends. It takes over 200 hours of one-on-one social time to turn a stranger into a best friend. If we don't keep investing time in our friendships, the emotional quality of these relationships decays very quickly, except in the case of best friendships, which often last a lifetime. We tend to meet our lifetime best friends in our late teens or early 20s. Best friends have an enormous influence on our mental and physical health as well as our well-being.