When did comic book deaths become meaningless

[Tzigone]

Obviously, when they became over used and there were fakeouts and actual resurrections as a consequence of too many deaths of deaths of too-important characters. I know it was 1980s for Jean Grey when she turned out not to be dead, but did she set a trend for non-belief in deaths or did that take longer? I'm not asking why - I'm just looking for a certain year or certain event that changed reader mindset.

I started reading comics in 1994. Marvel at the time. Reed Richards was either lost or supposedly dead, but I never considered it would last, and neither did anyone I saw post about it online. By time I got into Spider-Man, Mary Jane had miscarried, but there was some discussion on message boards of people who didn't buy it. So when did the day come when no believed death without hard evidence (and even then didn't think it would be permanent)? Certainly, these examples were both after the Death of Superman. And I can't think anyone expected that to be permanent. To be fair, he's an absolutely major character, so did the same rules apply to B-List heroes then? The idea that dead didn't mean dead forever?