Is it possible to whisk egg whites too much? Just a though that I had today while whipping egg whites in the tabletop mixer.  Can you whisk them 'till they separate, curdle, develop off flavour, strange aroma or texture ? 

Suppose they could cook from the generated heat if you'd whisk them for an hour or so, but I'm thinking more short term.
If you whisk egg whites to much they will definitely separate.

Basically you are over tightening their stretchy proteins which squeeze out all the water. You are left with useless protein fluff floating on water.

The flavor and odor will not change, however. That would be a sign off spoiling and unrelated to the whisking.