The strange feeling as the title suggests is quite strange indeed. I am a big fan of it, and I experience it quite a lot. The familiar sensation of your eyes burning while they become blood red due to lack of sleep, and the momentary lapses of concentration are the fun parts of the strange feeling. As against common belief that this occurs only when a person does not sleep for long hours; the feeling creeps in even if you have had terribly low amount of sleep.
As an example, I was up till almost 6 am yesterday night working on my internship homework [Yes, I do pile up my work till the very end :P ]. I had to get up at 8 and push off for work after that. The feeling had crept in once I got up from bed. The following data is what I have collected from all my strange feeling experiences. The times that are given are approximately after 20-22 hours of lack of sleep, followed by a maximum of 2 hours of sleep.
0-2 hours: During this time, a bath or the simple act of washing your face can make u forget the feeling, although the burning eyes are hard to get rid of :). Interestingly, your calves start hurting a bit, I have never understood why.
2-4 hours: This time is the best, the feeling does not interfere in your normal work.
4-8 hours: The feeling starts returning, and a nice lunch can solve the issue; considering in my time table this is lunch time. The lunch gives you intense satisfaction, but then leads to a strong pull to sleep.
8-12 hours: This a generally lazy time. It is hard to do anything productive in this time, and there is a slight risk of going off to sleep.
12-14 hours: This is the toughest part. You will feel sleep overcoming you so strongly, that most novices can’t get past this point. Even veterans sleep for sometime at this point if they have nothing interesting to do :)
14-18 hours: Once you are past the 14 hour mark, its a easy ride for sometime, a good meal [not too heavy, too heavy meals are dangerous :P ] can help you concentrate here.
18-24 hours: This is the fun part. You start feeling you are in a dream sometimes. Your mind slips in and out of reality as it plays games with you while you work. The lapses in concentration widen, and it takes some time to get used to this. I would not suggest driving past this point, unless you are taking strong help from caffeine :)
24-30 hours: This is where you can work, but this is where I start thinking “why the hell am I awake for so long? Nothing is this important” My limit is reached somewhere around here, and I collapse, and give in to the strange feeling.
Right now I am at the 15 hour mark, and relaxing, writing my blog, listening to music, as I prepare myself for the ride ahead. As and when I reach new points, I shall release a new version of this post, with my new experiences.
PS: Anyone who has reached further, which I am sure most of you must have, kindly let me know of the dangerous points of time to stay alert :P