My DD in Y4 will often talk about her best friend... her best friend in her class, her best friend on our street, her best friend at dance, her holiday best friend. A week ago DH said to her, "they can't all be your best friends" and she said "they're all my good friends" and tbh that's the way I remember feeling about my friends at school too.
The one who probably was my school most consistently close friend went a bit distant on me when she started hanging around with this 'cooler' group and although I was kind of welcome to join too, they found me dull and I found them pretentious. I was a bit snotty about it and friend blanked me for a few days. We probably weren't so close after that but years later we are still friends and see each other whenever we're in the same locality (not often but maybe a couple times a year).
I have a close friend from uni and we do chat and message a lot - but if either of us didn't message for a few days we'd think nothing of it and probably wouldn't notice. He and his partner usually have Sunday brunch with us so I'd find out then if something was wrong with him! There have been times when one or other of us has cancelled it several times in a row - busy, tired, unwell, distracted, other commitments - but I don't think either of us would read more into it.
I don't know - I guess I just feel that friendships work when neither party is obsessively emotionally invested. But equally, it's not very nice if people blank you or start acting distant for no reason. I don't think running after them will help though, because ultimately it's got to come from them and there's no point trying to force it.