Casual straight razor user (mainly traveling to avoid overloading my suitcase in my electric razor), I am a huge fan of Mach 3 blades, normal or sensitive. An excellent fit thanks to the three blades, a life superior to the competition. I use them a dozen times generally (two weeks with rarer shaves the weekend) and, indeed, they take the duration as well ad the box.
Big advantage of this package, it is not overpaying by buying of a sudden a dozen blades, with savings in the key. A big plus