Depends on the blade. I just ditched a Polisilver after 32 shaves so ten blades could easily do over 300 shave-days. The Voskhod that went in next will if i push it, go for four so-so shaves, so ten of those 40 shave-days.
dave
dave
Around 2 years Astra face shaves.
At least 2.5 years Polsilver SI face shaves.