the degree to which sleeplessness not only is impacted, but can impact daily functioning/state of mind is, in my opinion, greatly understated/misunderstood.
The longest I've gone with no sleep for me was 4 days twice. I only count the second time though, since the first time It was kind of my fault for screwing around taking adderall for 4 days in a row. At the time I was doing too many drugs for my own good and not much else so that was a result of that.
Anyways, the one time was more recent and it was on a very bad road trip I went on. I finally got some sleep soon after it got so bad I was hearing things. Things looked a bit weird to but I am kind of used to that since I generally don't get enough sleep and when I do I either wake up repeatedly or just have terrible dreams all night if I dream. The only way I can really describe how the lack of sleep feels is like a bad psychedelic trip but maybe a little mellower since I am not always in the corner afraid to move.