Ask yourself the following questions:
(a) How often do you wet-shave your face/head/legs?
(b) How many shaves on average do you get from each razor?
If your answers are (a) 3-5 times a week and (b) around 4 to 7 times with the same blade and you are male, you fall into the average usage category. As you would expect, the lifetime of a razor blade varies according to the conditions it is subject to. If you are female and you only shave your legs/bikini line, the usage will be less frequent and blades will last longer. However if your hairs are darker and thicker, your blades will need to be changed more frequently. Either way, it would benefit everyone if there were a way to extend the life of the average shaving razor.