Don't shave so often! No, really.
The key to a much better shave and razors that will last forever is to not shave every day!
Contrary to what the razor ads tell you ("change razors for a cleaner shave") the best way to have a well toned face is not putting new blades to it and shaving less often. A longer beard is much easier to grab with the blade!
My advice: do not shave more than thrice per week and you'll never have to buy a new razor! and people will also get used to more manly looking men!
I've been regularly using the same Mach3 razor (three times a week) for about a year before changing the cartridge (for over five years now), with no complaints from anyone! And my face loves it (and less blood than ever!). The face never looked so good while shaving every day! I think I'll decrease my shaving now to twice a week! Sundays (I'm a priest) and Thursdays. That should do wonders!