Two letters

Every time I see a chain of two-letter words in an english sentence, I wonder what the maximum length such a chain can be, and still have meaning.

My rules are: You can only use a given two-letter word once, you cannot place any punctuation between the two-letter words, and the sentence must make sense (i.e. be something someone might actually say).

The longest one I can come up with right now is:

"What can we do if he is to be on or in it at an unknown time?"