Blades used to last a week or so in The Seventies. Why? Because shavers used to do a one pass shave, maybe a second shave in the evening before going out.
Now I do a 3 or 4 pass shave for 2 or 3 days, the equivalent of 12 days shaving, back in the day. Simple.
Very true. Also, almost all blades in the UK were British-made, and, judging from the few I have left from the late 60's and 70's, were generally a superior product to most of today's blades, most of which are foreign-made.
Nowadays I throw out a DE blade after three uses, and they are cheap enough to do so. Back in the earlier times, and bearing in mind that my starting salary, in my early 20's, in a London advertising agency, and living in London, was £507 p.a., razor blades represented a significant expenditure, so I eked them out for at least a week or 10 days. Then I grew a beard, but that's another story.