2 or 3 shaves occasionally 4 sometimes 1 for me it depends on the feel of the blade.
I usually replace blades after ~ 7 uses, but that's because a week is a convenient marker, not because the blade is already giving me trouble. Call it pre-emptive maintenance. Who wants a failure out of the blue?I'm truly fascinated by the widely varying experiences of how long a DE lasts for different users. Personally, I find it takes 1 - 3 shaves for a new blade to settle in, after which I'll typically get a dozen or more shaves before I get bored with it and want to move onto something else. I'm guessing that the "settling in" process is the coating on the blade being worn away and/or smoothed out so that's its no longer impacting the blade/whisker interface. Regardless, I feel a blade is hitting its stride when others think it's ready for burial.
I've only rarely stretched a blade to see how many shaves I could get before a clear degradation, and I haven't counted, but it's more than 40, I think. And some here get way more than that.
Blades are cheap, and this is a hobby where clearly there's no right way. Anyone else can use multiple blades per shave if they wish and I won't accuse them of "doing it wrong." But I'm still curious about our widely varying experiences. Whisker toughness and density would seem to be the primary variables, and prep + technique no doubt come into play as well. Is some of it psychological, too? Probably, but that could also imply that I'm refusing to recognize the degradation of my well-used blades out of some sort of stubborness. (Who, me?)
More generally, while we all really enjoy shaving, I am amazed at our lack of consensus on just about everything. Does "YMMV" prevail to the same extent in other niche interest groups?