I use a blade for a week and change it out every Saturday. Interestingly, when Alcatraz was a Federal Prison, the inmates were issued two razor blades every Saturday. They were requited to be clean shaven every day and had to turn in their two used blades to get two new blades each week. Having more than two blades in your cell or in your possession got you thrown into an isolation cell. If you refused to shave you were thrown into an isolation cell and forcibly "dry shaved" every other day until you began to shave daily.