Okay, so Turtle has too much time on his hands. However, he's on to something. I have started to mark my blades with a Sharpie marker with simply a dot for every shave. My present Timor blade has 4 dots. We'll see whether I can go to a 5th shave or not with it. I often can't remember whether it's the second or third shave for a certain blade. That's why I started the dots.
I like the sharpie idea. I'll give it a go. It's hard to keep track of what pass you're on if you have multiple razors loaded with something different.