The longest I have gone without sleep is 21 consecutive days. Nobody believes me but it's true. I was pretty well gone by that time - brain not functioning, hallucinating, seeing my dead relatives round the foot of my bed. Not a nice experience.
I have had serious insomnia for over 20 years and have been on benzodiazepams all that time. I now take 10 temazepams a night, although they're not working, as I haven't slept in 6 days and counting. My doctor thinks thay may be having a paradoxical effect - sometimes you can get so used to them that they actually start to keep you awake, so he's trying to cut my dosage down gradually.
As to why I can't sleep - I have an extremely active mind that just won't shut up day or night - I only need it to be quiet for 5 seconds and I will fall asleep, but can I manage it? - no way.
I'm going to pursue meditation next, as this can lead to a better control of the mind and could be the solution.
Keep you fingers crossed for me.