how many shaves?

[Minnow]

How many shaves do you typically get out of a double edge razor blade?

[rockviper]

This is one where YMMV comes in strong.
Derby and Shark - 3
Astra SP and Feather - 4
Rapira - 5

[jtb]

I usually only go 3 shaves no matter the blade. They are pretty cheap afterall.
But this is truely a YMMV topic.

[jcwit]

Anywhere from 3 to 5 depending on the blade.

[Wetshavemike]

Depends on the blade, but usually 2-4 shaves. If something seems off, I toss the blade. When you buy them in bulk, on sale, it is not worth pushing a blade beyond its prime.

[BrianK]

I've been in blade testing mode for 3 months now and I'm keeping detailed records. I use a blade up to the point where it really shouldn't be used anymore then can it (literally). Some blades aren't good for even one shave, but that's not what you're asking about.

Feathers are excellent blades and give a great shave twice for me. A 3rd shave isn't worth trying for. Then in the other extreme there are Personna Medical Prep blades; I gave up out of boredom and I had 8 great shaves on the blade. There are a few like that. I figure in use I'll just use them for a week and change them.

So to answer your question directly, with blades someone would willingly choose to buy and use, from a low of 2 shaves per blade to at least a week if one shaves every day.

You didn't ask about Single Edge (SE), but they are on the high side of longevity. The SS blades I've gotten from CVS and Rite-Aid uniformly go a week per blade, at least for me.

[KM-instructor]

2-3-4 depending on blade of choice, like others have mentioned here , they are cheap enough to replace whenever you feel the need to change them.