Hallucinations start after 3-4 days. You risk sudden death any time after 5 or 6 days. That doesn't mean death happens, just that it could. The strain on the body is high so the heart and lungs and stuff can just suddenly stop working, especially if things like caffeine are involved. That being said there are plenty of people with insomnia that last for about a week without stimulants and therefore are safer then the rest of us. All and all the only thing guaranteed is that at one week you'd be seeing things.
After a point your brain will force you to shut down no matter what is occurring also... with the average person three to four days is all you'll get before your own brain pulls the plug.