I always dry off my Mach 3 blades after each use, but I they don't last me a whole year or even close! Sometimes, I will use a trick that I read somewhere:
Set a pair of blue jeans on a flat surface and run your blade (in the opposite direction of the cutting edges) along part of the denim 10 times from left to right, then 10 times from right to left... this really does work to sharpen your blade and make it last longer. I rarely take the time to do it, but when I do it, I always wonder why I don't do it more often... if not every time.