The metal ones seem to last pretty well forever if you take care with them. I still have some old Kodak cassettes from the Panatomic X and Super XX days, and they still work well. I also have some I bought about 25 years ago, and they still work well.
I also use mine again and again and they seem to last forever. My newest ones are 3 years old and they are fine. I just give them a blow before I load the film.