Theory #1 - The sharper the blade the longer it will last because it dulls a little each time and therefore stays usable for more shaves. Theory #2 - The sharper the blade, the thinner the edge and it will deteriorate faster than a blade that starts off duller and thicker. The reasoning here is that the thinner one is more fragile and easier to break apart to an uneven edge in the way a very sharpened pencil will break easier than one that writes well, but isn't sharpened to such a delicate fine point. Which is it? Based on my verrrrry limited experience thus far I'm leaning to #2. In the end, I haven't found any of the four brands (Astra, Dorco, Wilkinson, Derby) I've become familiar with to date to be all that good after day #3 even if it remains somewhat usable in some cases. The sharpest seem to be the Wilkies and one of them only made it through two shaves well although the other Wilkies were decent enough through Day 3. Astra SP is my fave so far, and it's not really close. The contest, that is, not the shave! Edit to add: Should have been posted in Safety Razor section. Sorry about that.