Fantastic reply!
While it can be argued that there were major shifts beyond the Bronze Age,
the question is whether introducing some other metal is the appropriate way
to signify the 4th, 5th, or 6th shifts for comic books? I don't think so.
Looking to radio and television as examples, I don't think I could even describe
the Silver Age of Radio... much less what comes after Bronze, if there is one.
At some point, Television becomes "Television of the 1970s", "1980s", etc.
Everyone knows what you mean inherently when you talk about the 1980s...
you name the subject: television, comic books, sportscards, politics...people know.
Even the indication that this hobby isn't sure when the Bronze Age ends
signifies to me that the concept of the "Age" is outliving its purpose.
When do the 1970s begin and end? That's easy. The 1980s? Again, no problem.
In fact, what is the first thing you have to do to describe the Silver Age of comics?
You have to describe the years it covers. Then there's the inevitable question,
"What's so important about 1956?"
At the end of the day, even the Silver Age isn't "one thing".
Marvel 1968 is very different than Marvel 1962.
In essence, Marvel in the early 1960s differs quite a bit from Marvel in the late 1960s,
even though it's all "Silver Age".
While some might consider "comics by decades" to be a dumbing-down of the hobby,
it seems unavoidable. There's already no way to describe the Bronze Age without
some mention of the 1970s and some debate about the end of the Bronze Age
occurring either with the end of the 1970s or early in the 1980s.
Golden Age - you bet... even Atomic Age, if you like.
Silver Age - ok... I think I know what you mean, even though Marvel is later than DC.
Bronze Age - makes me think of Conan, bronze sword and all, but ok... Bronze Age.
Copper Age? Chrome Age? Do you mean the 1980s? Well why didn't you say so.