> isn't the definition of a bubble that it pops quickly?

There is no consistent definition of a bubble. We have no fundamental reason current valuations have to collapse suddenly.

Is there any definition of bubble that doesn't involve popping? That's literally the metaphor.

> We have no fundamental reason current valuations have to collapse suddenly.

I would agree, but i think that is just saying that the current situation is potentially not a bubble. Which may be true. We will only find out after the fact.