The one time I took DOC, 2mgs, I was unable to sleep for TWO consecutive nights, and even after waking up after the third night (and first night of sleep) I definitely felt the unimistakeable nootropic signature of a tail end DOC trip.
I'm not a pharmacologist but I think there's got to be an enzymatic difference in some people that makes it a lot toughter to clear this chem from the body. My girlfriend was sleeping like a baby at hour 14 while I was fully dilated, stimulated, diarhea, +3 tripping. Also, I have no trouble getting to sleep after acid or MDMA at a normal time--I can slip into sleep while coming down from a roll or acid by taking deep breaths and entering that dream state. On DOC though, even by night two, I was just way too stimulated.
My advice is, if you haven't experimented with DOC, make sure you have three full days to recover. I had to call in sick for work, at a job I could handle on acid, no sweat. The insane head I had on DOC would NOT have allowed me to function in society, though, at all. I was bonkers.