I too usually get 20 or 21 shots on a 36exp film.
My tip: when the frames-left counter reads '1', try switching to standard framing and seeing how of these are left. When the counter reads one panoramic frame left, this means it cannot fit two panoramic frames on the film. Once the photo has been taken, the film will finish. BUT one panoramic frame left might mean there is just under 130mm of film left (2 x 65mm). In that same amount of film you could take three 36mm frames, or even one 36mm frame and one 65mm frame!
This is of course the worst case scenario at the end of a film, but it does mean you can get two or three shots for the price of one!