How long does a virtual friendship last? 

In the age of Social Media, the more friends you have, the more you are popular. 

When we accept a friend request, automatically that person, often unknown, becomes our "friend" (maybe in real life we ​​don't even say hello) until one of them gets bored by clicking the "Unfriend" button and then become perfect again unknown. 

How long, therefore, does a virtual friendship last? One minute, one day, one month, one year...

or forever?