I don't believe an era is defined necessarily just by members.
I described the Beatles
Bee Gees: pre and post Saturday Night Fever
U2: lot of eras
QUEEN before and after The Game = 70s and 80s = not synth and with synths
etc...
even singers may have different eras:
Olivia: pre and post Grease (confirmed by herself)
Elton John
David Bowie
Rod Stewart
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