Sentence examples for but how long from inspiring English sources

BUT how long can this go on?

But how long is that?

But how long, and how much difficulty?

But how long will this tradition continue?

But how long will the romance last?

But how long will it continue?

But how long can these tests take?

But how long will this continue?

But how long can that last?

But how long could that last?

But how long can one last?