I reuse the multi blade ones for quite a while - months each. They stop working because the blades get junk between them, not that the blades get dull. To remedy, strop them backwards along your arm to clean the junk out, only a few times seems necessary, then give a rinse under the tap. I just do this out of habit each time I use them now - they last a long time.
If everyone knew and practiced this, the razor blade industry wouldn't be a billion dollar industry. People would buy an order of magnitude less blades. The maintenance takes less than a minute, and is only necessary once every two weeks (if you're a weekly shaver). As you say, stropping will make the blades good for months.
