8 months. That's how long I've been using my most recent Mach 3 blade.
New razors are good for one shave, then they are as shit as old razors, and my stubble grows fairly thick.
P.S. Shaving foam / cream. Pointless waste of money.
Soap does just as good a job, if not better. Don't get me started on after shave moisturising balms or any of that shit! Do I ever moisturise anywhere? No, the only cream I use ever goes on my gooch! Why would I want to moisturise when I shave? puts foot through TV