Does anybody know how long a mach3 (I thing there called M3 nitro) blade is meant to last or how many shaves per blade. I currently have a packed of 8 that seem to only give me one or two good shaves at the max. After this the alo vera strip gets very rough and it gives a very uncomfortable shave and therefore thrown away. Is this normal or just a bad batch. When I used the normal mach 3 blades everything was fine. I will be going back to the normal one but was wondering if anybody had the same experience.