Stephen LeBerge, I think it was, did a test. He had someone sleep, and in there lucid dream they were to blink (which translates to waking life, as the body does not paralyze the eyes, thus allowing "Rapid Eye Movement") at a set interval. I don't remember the exact results, but it was pretty much on scale with waking-life time.

Though it may vary from dream to dream. Many propose that "time stretching" in dreams is simply an illusion by the mind. (Just like how movies can show you a "years worth of time" in an hour and a half)