The Powers That Be used to opine that the everyday comic book fan was tripping through a perpetual three year revolving door, eventually stopping collecting as they became older. I used to suggest that if a reader stuck with it for three years they might drop collecting but would retain a peripheral interest in the hobby and even purchase the odd story occasionally.
I don't think there's a revolving door any more as the companies have done their level best to destroy any entry level for kids and the only people that are still buying comics have been doing so for the past ten years already. I could be wrong but I don't see many humans under the age of 25 looking through our 50 or so thousand back issues.
Yes, yes, "Graphic Novels" are another story. Still...