Dave, I can't do that wrote:
Hi guys,

OK, a bit if a cheeky Subject to keep it metalworking oriented.

I have had a full beard for around 40 years. About 6 months back I
shaved it off and had been using a Braun electric razor up until a few
weeks back.

Since then, I have been using a disposable double blade (20 for 2-
bucks) for about 4 weeks and it still seems to cut fine. When I last
shaved 40-years back I seemed to recall changing blades in the old
Gillette screw handle every few days.

So, finally to the Subject, how do I tell when these disposable things
need tossing?

Every few days I take a single swipe with a new one and still cannot
tell the difference in cut or feeling.

I recently bought some Wilkinson Sword razor blades which have a kind of
ceramic coating. I've found that they last much longer than cheaper blades.

Best wishes,

Chris