andrew027: Reading this thread makes me feel positively out of touch. I hate shaving and wouldn't bother with it except my beard coverage is poor - I can get away with a goatee but any hair growth on the sides just looks a mess. I shave three or four times a week, less if I'm on holiday. I have a Gillette Mach3 handle that must be at least 15 years old and buy an 8-pack of cartridges at the supermarket for around $35. I get between two and three months out of one cartridge, so the 8-pack usually lasts me 18 months, or a bit more.
Either your hair is very soft of you are very tolerant of crap blades.
I would get maybe 3-5 shaves out of a cartridge before they got blunt.