When is an IPA not an IPA?
When its lost a substantial amount of its freshness and sinks to the level of a pale bitter or bitter pale.
What a loaded question...you'll get different opinions on this one, I'm sure.
I like them highly bittered, highly aromatic, and unlike most of my friends here on the boards, I like them fairly well aged.
But the style is (and always was) open to wide interpretation like any beer. Add to that the fact that most of what we have all read about IPA is evidently incorrect anyway, the answer to the question posed really becomes "who's to say?"
It all just de[ends on what you like.
Since there are no rules carved in stone, it's an individual thing.