What's it like to have the same friends from early childhood well into adulthood?

I saw a meme once that showed two boys walking into a wood. The caption said, "The day you spent with your best friend, not realising it was the last day you'd ever play together."
It didn't mean one of them died, it means there does come a day, for one reason or another, that you played with a friend for the very last time, without realising the importance of those last few hours. It made me think about all the friends I lost touch with.