Not sure I have really done a tolerance break. Certainly nothing measured in weeks. I am glad I don't have to quit for weeks, my sleep would be buggered but good, and not because of nightmares, just because of ongoing brain rattle that refuses to settle down. Pain in the butt until I tried weed to see if it would help, and it does,
In any case, lack of weed certainly brings on vivid dreams, but for the most part they are tolerable or fun for me. I can't recall any nightmares. OTOH, my hair color is not known for being a symptom of good memory, even aside from the weed.