How much “old” do you need?
That question was more hypothetical back in the spring, before DC’s “Rebirth” initiative started quantifying it. “Rebirth” was as direct a response to the New 52 as the publisher has ever given, even bringing back specific characters from the old days to help the healing process along. “Rebirth” also up-ended the normal relaunch paradigm, which seeks to streamline a character’s presentation so as to keep what works and discard what doesn’t. By contrast, “Rebirth” took the position that the status quo generally needed fixing, and specifically could use a healthy dose of what had come before.
Regardless of its inelegance, though, the New 52’s streamlining had to come from somewhere. The old regime had been in place for at least 25 years, ever since the great cosmic streamlining of Crisis On Infinite Earths. Back then, the question of “how much old” related to what the character could do without. Today, it seems like the question is what the character needs to have put back.