Braun actually state that they design these to last for 7 years - based on a daily shave of course that would be 2,555 shaves, but I rarely shave everyday so I would expect to at least quadruple that figure
I usually prefer a wet shave and have used those Mach 3 (really?) razors with 4 or 5 blades in - but honestly the prices of the blades are ridiculous now £9-£12 for a pack of 4 or 5 blades.
I lasted all of 2 days with el cheapo throwaway jobbies and had a face like Edward Scissorhands had been let loose on it after a few whiskies - never again.
My Philips from about 20 years ago is still working, but as that takes ages now - with shaver rash after - so I can't be bothered with replacing the heads on it at this stage as it still takes ages to do a proper job.
I'm going for the 9290CC with the clean and charge station that disinfects, cleans, lubes the blades and dries all in one. Plus I can use Gel or foam and use it in the shower / bath as it's a wet and dry one. I know I'm in for a world of pain with buying the alcohol based cleaning cartridges, but again, I'll probably clean it the water and give it a thorough clean in el machino once a week - and that will stretch out the cartridges a bit longer