I recently came across a way of sharpening (or more correctly, honing) blades which promises to drastically reduce the money I spend on blades. It's simple, but remarkably effective.
- Get an old pair of jeans
- Gently run the blade 30 times up the jeans (about 10 or 15 cm)
- Switch the direction of the jeans (so the grain is pointing the other way).
- Gently run the blade 30 times up the jeans again
Remember not to "shave" the jeans, and you don't need to press down hard (I just use the weight of the razor). This process hones any nicks in the blade and polishes them. Using this process, I've been using the same blade for one month now, and it shows no sign of losing its effectiveness.
Of course, you'll lose the comfort strip, but this isn't much of a loss compared to the savings you'll make.