I get that you're a numbers guy, but Art and Literature are almost universally categorized by eras and genres, not decades. Try to put Ingres and Delacroix in the same room and tell them they're both 1820's artists. It'd be a brawl. Comics are both Art and Literature, so it's only natural that fans/scholars would categorize them the same way. As one of the most knowledgeable members of the boards, your time and input would be quite valuable by contributing to the discussion of which characteristics (beyond New Year's Day of 1980 and 1990) help define certain time periods rather than just stonewalling it with the same response.
I think he has a point. I used to be a big "ages" guy but when you figure in that there is disagreement about ages in many cases and the fact that certain genres don't even really fit into an age, then it makes more sense to just go by dates. Saying "1980s comics" or "1960s comics" has meaning. There is something there. That type of change is worth discussing. However, even going by decades is not without it's own issues. No method is going to be perfect