I used Astra SP only twice, used for 3 shaves then tossed it. Maybe it should last 4 or 5 shaves but I have several brands of blades to try and by force of habit I throw away the blades after 3 shaves.
I dispose of the blade after 3 shaves and they're still absolutely fine. I've no doubt I could go more if I had to.
For info., that's with very soft water, shaving every day and a not particularly heavy beard.
I choose to do 3. This usually gets me through the week (I shave every other day), and with blades as cheap as they are, why bother pushing it. Besides I like loading up a new one
I get one use, I shave my face and neck first then I shave my head. After the head the blade is pretty useless for another face shave although I could get another head shave out of it...but what's the point at less than 10 cents a blade.
I have a mustache and a bit of beard on my chin, so I normally go a full week with one blade, including shaving the back of my neck free of fuzz before changing blades. I suppose I could stretch the time before I feel any negative effects, but why bother? I have hundreds of Astra blades on hand that all cost less than $10/100 including shipping.... The first shave is very good, and the second to last shaves tend to be just fantastic. I also enjoy using several other premium label blades, but the Astra is my all time value priced favorite foundation blade..