I just read somewhere that you shouldn't use the same straight razor two days in a row ! Is this true ?
It's a good excuse to have more than one razor in your inventory if you ask me. The best thing to do is try it out for yourself. Use the same razor for a month, then switch between razors for a few months too. See if using it over and over has any effect on the quality of shave you get. Also, If your not honing your blades yourself, it might be a good idea to have 2 or 3 blades so that when one is away getting sharpened, you still have a sharp one to use.

Be warned though, once you start buying multiple razors, its hard to stop. Good old RAD will grab you and pull you in with its tractor beam.