What’s in a retcon, anyway?
The more I think about, the less I believe that comic book writers feel compelled to be bound by earlier writing. Unless an editor is keeping them under their thumb to get coherent writing – and if DC had that, things wouldn’t be such a mess – it seems to me they are happy to blend their personal variant of a canon backstory. I will present a number of examples to support my hypothesis.
Pre-Crisis, Marv Wolfman wrote Dick saying he was Robin from age 8 (New Teen Titans #39, 1984), and he’s about 19 at the time.
New Teen Titans # 39. By Marv Wolfman, art George Pérez. (1984)
When Crisis on Infinite Earths reached Batman, Jim Starlin wrote the retcon that said that Dick was Robin for six years, presumably from age 13 to 19. (Batman # 416, 1987). This version also included that Bruce fired Dick from Robin, but more on that later.
Batman # 416. By Jim Starlin, art Jim Aparo and Mike DeCarlo. (1987)
And then Marv Wolfman wrote Batman Year Three (Batman # 436–439, 1989), and all of a sudden, it was ten years since Dick’s parents were killed when Jason had recently died. That has to imply that Dick was Robin for longer than six years, right? And that Dick was about ten when he came to Bruce.
The following year, 1990, Dennis O'Neal wrote an illustrated short story about Dick’s origin where he was ten when his parents were murdered. (The Glimpse. In Secret Origins vol 2 # 50, 1990)
Dennis O'Neal, by the way, was the editor of Batman # 416 and co-editor of Batman Year Three (Batman 436–439). He should be the guy to keep track of details like this, shouldn’t he?