Will Karma 'balance out' in most cases by the end of a lifetime?

So, let me start with the disclaimer that I am not a Buddhist and I am just asking this to further my understanding. Either way, the thing I was wondering about, does Buddhism hold that in most cases karma will balance out within a single lifetime? Or will it only balance out 'in due time' which could be after many many rebirths? Reason I am asking is because for Buddhists I 'know' (no actual friends) they always seem to live in the expectation that it will soon balance. To me that entitled behaviour is always incredibly off putting, but that's **not** the point, I am just purely curious whether the expectation (not the entitlement) actually makes sense at least from a theoretical Buddhist believe point of view.