If your my dad you get 30 or 40 per blade.... bought him gear for fathers day last year. He just called to tell me he got through his first box of 10 blades. They were merkurs...
i only use vintage [tungsten] personnas nowadays and could easily go 20+ shaves per blade; the 'comfort zone' just starts to taper off around 12 - 15 shaves so change blades then.
i reckon if you didn't have a very heavy beard and only shaved on weekdays for work, a 10 x pack of personna 74s could almost last you a whole year!
Most blades can give me up to 4 shaves the 4th mediocre, so I just change after 3 which most blades are capable of. Theyre so cheap I don't really think about it
Singapore thins: 3 @ five cents a blade or 1.6 cents a shave. Why try for four?
Personna blue: 2 Ironic isn't it?
Pol Silvers: 3 at 38 cents a blade-that's 12 cents a shave.
Personna reds: 2 (forgot cost per shave.)
I never have counted. When any "blade", including modern cartridge devices, ceases to offer a good shave, then I change it. I believe it varies by time of year and personal schedule. If I have taken special care to be really sharp looking, closely shaven, then I made extra passes, and two such shaves may put as much wear on the blades as three of my more usual shaves.
The last month, more or less, I've had at least three DE razors, each with a blade in it, and an SE razor, and an Injector razor, all getting turns in no particular sequence, just however I feel at any given moment (I've also used my Sensor, and a TracII cartridge in a Bump Fighter, for some cleanup under my jawline). I've not made any effort in the past to count shave numbers, and the current situation would make it even more of a chore to do so, and I just don't need to worry about it.
I have been straight shaving for a while now, but when I used DE I would toss after 3 shaves (Feathers). I can probably get 1-2 more shaves if I had to, but why? DE blades are cheap, besides I am saving so much money in this hobby
4 is my 'industry standard'. I tend to use Derby's and Timor's, I flip them after each shave. I have on occasions stretched them to 5 and very rarely 6
I can't help but think of the thread someone wrote about their Dad being a shaving meiser and I wonder if I'm not there too because I'll use a blade for about two weeks of daily shaving before tossing it.