I haven't slept for ten days...

I haven't slept for ten days, because that would be too long.

This is a line from a stand up comedian, Mitch Hedberg (warning, he has some foul language, so I wouldn't really recommend him to those who don't like that stuff.)

The humor in this statement is based on the fact that the listener understands the first part of the sentence incorrectly until they hear the second part. This is called a "Garden path" sentence.

A naive reading would be "I haven't slept for [the last] ten days [before today]", when the correct reading of the fragment is more like "I haven't [ever in the past] slept for ten [consecutive] days".

The entire sentence, when read together is pretty absurd. Who sleeps for ten days? I suppose that the fact that Mitch is on drugs is probably why he comes up with such oddities.