If pandemics die out, on average, in 1-2 years, wouldn't this die out anyway on that timeline?

We're already up to a year and a half, so if it's gonna die out then it better get a wriggle on!

Or will it be like the flu - where new strains (and new vaccines) go on forever?

This is where the man-made aspect comes into it. If it's not natural, then it may not die out naturally. Those still denying the possibility of a lab-leak always mention that coronaviruses jumping from animals to humans are relatively common - what they fail to mention is that the vast majority are harmless - certainly nothing like this has ever happened with a coronavirus.

So that puts us in uncharted territory.