wouldn't once imagine

[KLPNO]

Hello everyone
I'd like to ask about the meaning of the phrase "wouldn't once imagine" in the following context.

And he had a conventional family who promised him that the trade winds would soon weaken and the Continent would push its way back to its natural location. What was dead now would live again, those trusted voices argued. The dark lands would grow again. And because he was young and naturally optimistic, Jopale cnvinced himself that he would live to enjoy that glorious rebirth.
But the boy grew into a rather less optimistic young man, and the young man became a respectable and ordinary teacher of literature. During the average cycle, between one quiet sleep and the next, Jopale wouldn't once imagine that anything important about his world could ever change.

Does "would" in this case express repeated actions in the past?
And what does "not once imagine" imply here -- that he imagined more than one time, or that he did not imagine that at all?

[Anglika]

It is referring to the period of the cycle, during which he would not [did not] at any time imagine that his world might change.