forever; without success, no matter how long one perseveres.
He can continue to be hard on himself until hell freezes over, because he's so self-centeredly pessimistic that there's nothing I can ever do to lighten him up.
They can be bellyaching to me about their life's problems until hell freezes over, but it doesn't mean that they'll ever get my sympathy.
I am prepared to wait for my answer until hell freezes over.
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