Han only changes his suit FOR(!) TESB and then got teh old one back in ROTJ. He didn't change it halfway the movie. They just took his jacket when they started torturing him.
And yeah, I think OB1 will wear his robes throughout the movie. Anakin wears several outfits, we saw that. It is very doubtful that OB1 will also wear different outfits since we never saw any other on any spy pic.
queeq out