When do I need to change blades

[Dave Q]

I foolishly thought I could get a fourth day out of a Rapira Swedish Steel. Yesterday I got a nice clean smooth finish, so thought hey I can get four days; I can with Rapira Super Platinum.
But it wasn't as good today. So will stick to three days for that blade.

 

[FrankieG]

I get three 3-pass shaves from most blades, although I can get 4-5 from a Personna Lab or Super Iridium.

 

[Curator]

The Dorco blade I tried was half my face.
The Gillette Silver Blue goes for about 5 days.

Each blade has it's own life. If I ever feel tugging or hurting, then I change the blade.

 

[49er]

An average of 7 or 8 pence a blade. Blades no longer being manufactured get 2 or 3 shaves otherwise it's one and done.