Started doing that a few years ago - I can get 3 (sometimes almost 4) weeks out of each razor. Normally schick, sometimes other brands (not Gillette anymore).
Found out it was mostly rust that was dulling them - so tiny you couldn't see it with the naked eye. Dry the blade, it doesn't rust nearly as much.
I don’t even know what brands I buy. They are the cheapest twins I can find at the Dollar General. I have got as much as 10 weeks on one, the average seems to be closer to six weeks. One of them was good for one shave- when you buy cheap the quality control is not so great. I’ve been doing it for twenty years give or take a bit. I try to keep it under a penny a shave. That’s all plus the 3 dollar hair drier, of course, and sales tax.