My friendships used to last 2 years, back when I was still capable of making friends. I once had a friend for 13 years. I can't believe it, it was either a miracle or there was something very wrong with her.
It ended when she had at last made better friends than me (or as someone above put it) allies, her values became more and more extremely socioeconomic and I was getting friendship crumbles. One day she overdid her typical coldness, I'd had too much, told her off and stopped answering her calls.
I've felt a lot better since, now able to develop myself in my own ways rather than being constantly trying to emulate her and her friends' socioeconomic obsession at the price of anything humane.
She knows she has a problem, but the world is so full of this kind of socioeconomic obsessed people that she's more popular being like that than not, so she has no motivation to heal that addiction. If she ever needs a true friend, though, she (and so many others I know) will be in trouble.
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There are two means of refuge from the miseries of life: music and cats - Albert Schweitzer