What are the properties of a long-lasting relationship? This important question as intrigued the social scientists during the last decades and has triggered numerous publications, surveys and experiments to detect what patterns are behind social relationships that persist. Probably the most famous finding is that of Granovetter who proposed that strong relationships are the ones more likely to persist in the future. And what is a strong relationship? According to Granovetter, a strong relationship is that with high intensity (a lot of interactions), intimacy (mutual confiding) and large structural redundancy (lots of common friends). ...