I'm asking this because I have a feeling that if I say How long has this been empty for? , It would be like an ongoing action. For example:
A: How long has the dog's bowl been empty for?
For about an hour (it's still empty).
But, I feel that it's "grammatically wrong" if I Say How long was this empty for? without having a time expression. But, if I say using the present perfect, it'll be an ongoing action (And I don't want this). I want to say this:
A: Fills the dog's bowl with food
A: How long this has been/was empty for?
B: For about one hour.
but if I use the past simple, I think it will be wrong.