Use 'never used to/didn't use to' when (i)the situation wasn't true in the past and (ii) it is true at the moment of speaking.
The prescription is implicit in the description - I think you're being a bit too, hmm, "what's the word", here.

You agree that 'most language classes do not provide a balance' of forms, but almost immediately after then question the relevance of my '23%'. Hmm again...
If "I wasn't always here in the mountains" sounds odd to you, you might like to watch (or rewatch) that scene in the movie.

I've hopefully said enough about how the moment of speaking is implicitly if not explicitly as much if not more the focus in the majority of examples (for instance, in 'I didn't use to be < >> this fat', the prior "slimness" is of course something that will come to mind, but the present size is clearly more the issue), but I perhaps should've said that the forms 'don't only "point backwards/pastwards" '. Perhaps you can dredge up reams of examples where they clearly and only do just that, but less lame/"incomplete" ones than variations on the one that comprises the thread title, please.I'm obviously hoping to strengthen my previous argument here (that 'didn't use to' and 'never used to' don't "point backwards/pastwards"), but would be interested to hear if I've overlooked something.
Of course they do.
I'm not sure what the point of your question is. The short answers if expanded would not require 'use to' before 'jerk off (3...)!', and are used in exactly the same way with simple past generally (He called you a *beep* - I never/I did NOT!); but FWIW I'm not sure I have a clear preference between the forms.Which answer, if any, would you commonly/automatically find yourself using?
Davy (to Suzy) Hey, Stevie used to jerk off three times a day.
Suzy: Really?
Stevie: I never!
Davy (to Suzy) Hey, Stevie used to jerk off three times a day.
Suzy: Really?
Stevie: I did not (didn't)!
No, but I do like them to sound like they're not from the mouth of some fey and forgetful f-wit. Glad you liked them, though!:lol:Your "overgenerates" example sounds like contextualised native-speaker English. Do you prefer examples and "rule" which undergenerate?