French language Q&A Forum

Recently while talking to a friend in French (she is native) I wanted to say something like "I never knew you used to do that!" and I used l'imparfait with 'ne ... jamais' and said "Je ne savais jamais..." because I considered it to be something ongoing or habitual in the past.

However she corrected me and said I should either say "Je ne savais pas" or "Je n'ai jamais su". In this instance, yes it probably would have been more proper in English to actually say "I didn't know you used to do that", however for futher investigation I tried translating the following negative statements (which express a habitual/repeated or ongoing situation in the past) and they all returned a translation using passé composé rather than l'imparfait:

"The guy I was dating never let me pay for anything"
"Le gars avec qui je sortais ne m'a jamais laissé payer..."

"I never used to eat olives, but now I'm addicted!"
"Je n'ai jamais mangé d'olives..."

"When she was studying, I would never see her, but now we catch up all the time"  ... etc etc

Is there a rule in french that the sense of "never/jamais" cannot be used in the imperfect past tense? Maybe it's grammtically incorrect and simply saying "I never ate olives" suffices here in French without needing that "used to" nuance that we have in english?

Thanks

Whilst not directly on this subject but is anyone able to explain the use of "vaut" from the example. Il vaut mieux le faire soi même.