Well it's one thing for writers to stay on a book, it's another if Marvel lets them. From a lot of different standpoints Dan Slott's run has been a major success for Marvel. Example: His idea for Spider-Verse got incorporated into a tv show in under 3 years of it being published.
But we should acknowledge that it's an outlier to have a writer stay on Marvel/DC book beyond 7 years. For Spider-Man alone JMS and Michelinie both lasted 7 years as the main guys on ASM. That's the longest run for anyone in the last 30 years on ASM. Bendis is a different case too cause he didn't write the same amount of Spider-Man comics that Slott has written in a 7 year span.
It's just kinda mind-blowing that Marvel would continue to let one writer stay on yet constantly change other books for different writers.