I've no idea if it makes me more or less suggestible, but I'm sure it has an effect :o I tend to get paranoid when I'm sleep deprived, which makes so I stay up until actual exhaustion kicks in.
Everyone needs differing amounts of sleep. I for one, can function as long as I don't need to do anything important on 4-6h of sleep, can function crankily on 8h of sleep, but am a proper person at 10-12h of sleep -- per 24h. A friend of mine however can be a proper happy person on 6-8h of sleep, and a research he participated in showed he sleeps very deeply, almost immediately. (I'm not jealous, you are :p)
I think the max amount anyone should stay awake is 20-24h. Of course, you can do more, depending on what kind of tiredness symptoms you experience. I suggest getting to the point where your body feels warm and you don't have anything to do anymore for the rest of the day. Not to the point of your eyes feeling heavy (unless suggested so~) That's already a natural state of relaxation, which might be preferable?