I just did the One Blade in February challenge and the blade had more life in it if I had wanted. Now, I do admit shave #1 on the next blade was an improvement over shave #23 on the older one, but it was a matter of degrees.I started just like you. One blade for a week. Then I found out that I could use for 2 weeks. It became normal. This year I am using a blade for 3 weeks and it has been like this for the last 2 months. I don't want to push for 4 weeks because otherwise I have more than enough blades.12 blades for a year is a dangerous thought.
Now I usually just let boredom tell me when to change. I have 2000+ blades so I don't have to stretch blade life out, and I do like variety.
