How long have you been to Hawaii?
I had a discussion about the sentence in the title and was told, the sentence is wrong or funny, or you do not say that way.
I think the phrase "have been to (place)" is used to describe an experience that you went to the place. That may be why the phrase "have been to" is not suitable to ask the term staying there.
In addition, I got this information. In this URL, one of the comments clearly say ""How long have you been to Australia?" is not correct."
However, I am not fully convinced. So do you think the sentence in the tile is wrong?
P.S. I am sure the sentence does not have any issue on the grammatical structure.