Stainless steel blade shavers like the slick marketed Quatro, Sensor or Mach 4 have blades that take a long time to go dull. However, they do tend to corrode if kept in untidy or wet conditions.
That is right! Some stainless does corrode in wet conditions. You see the blades are made of a certain type of stainless that is suceptable to corrosion if kept wet. The best thing you can do to get a blade to last a very long time is to keep it clean and dry.
When I finish shaving I take a spray bottle and clean out the blades very well by spraying directly into the blade cartridge to flush out the leftover shaving cream and whiskers. Then I blot the blade cartridge on a towel and keep it in the bathroom closet (NOT the shower)
Practicing this I have kept my Quatro blades in operation for 6 months at a pop, shaving every day of the week except Saturday.
If you are an experienced shaver you know the toughest spot to shave without nicking is the chin...so grow a goatee! Then you can get maximum life from your shaver blades and keep more out of the landfill. besides those shaving cartridges are expensive little buggers - Jason