not in a thousand years
Not at any point; under absolutely no circumstances. Not in a thousand years did I think that I would actually win the lottery! A: "Would you ever go on a date with Jake?" B: "Ew, no, not in a thousand years!"
Not in a thousand years! and Never in a thousand years!
Fig. No, never! John: Will you ever approve of her marriage to Tom? Sue: No, not in a thousand years! Mary: Will all this trouble ever subside? John: Never in a thousand years!