There’s a blue strip at the top of the Mach 3 razor blade that disappears/ wears off after several uses indicating that it’s time to change your blade, but it can’t be too accurate, right? It seems to wear down so quickly that I’m convinced it’s a scheme by Gillette to get Mach 3 users to buy more blades. I’ve been using the same blade for well over a month now. It’s a little dull, but it’s not like I’m shaving with a butter knife either. How long can you stretch the lifespan of a Mach 3 razor blade?