> When I'm really refreshed and interested and doing well and eating right I can pull all nighters and maintain work quality. I can't maintain this for extended stretches at all though.

I pull all-nighters regularly to work on personal projects, and managed to push out 4-6 hours of concentration during them after a full day work, but the key to that for me (with the caveat that I'm close to 38, and probably could push through more when I was in school, but on the other hand I know how to pace myself far better):

- I nap 1-2hour in the evening, after dinner, and then take a 1-2 hour relaxation period where I'll vegetate totally in front of the TV or listening to music punctuated by low-concentration tasks such as making a list of what I hope to achieve (with estimates and times at the night where I hope to get to them, which makes for a hilarious lesson in how bad we are at reliably estimating stuff...)

- I pump myself full of caffeine (usually about 200mg, my caffeine sensitivity is really low) and b-vitamins, and "dripfeed" myself sugar.

- I'll use modafinil to retain alertness when I go off for work the next day.

- I'll go to the gym but focus on cardio, stretches and time in the steam room and make sure I have time to take "the slow train" which gives me a 30 minute nap during my commute.

- I'll make sure to take a proper relaxing lunch break. Sometimes I'll go find a park bench and sit and nap or meditate for half an hour.

- I'll make sure to schedule my daytime work to the times that works best for me, and try hard to get some extra high concentration work out of the way on the "before" days, and do more "menial" tasks on the "after" days to ensure the overall effect on my daytime job is minimal (overall I think I actually end up with a net benefit, as the personal projects I work on generally are learning experiences that are often synergistic to what I do during the day).

- I crash totally the next evening - usually going to bed at 8pm and sleeping until 6am the following day. Everything in my scheduling is geared towards keeping me productive the following day too, but with the expectation that the evening will be totally lost.

- If I at any time see my productivity start slipping at night, I go to bed. If I see my productivity start slipping in my day job, I take a week or two break from this schedule and get to bed extra early, because I know if I don't I'll tend to get into a rut where things take longer and tire me out more, prompting me to get stupid ideas about working even longer. And I never, ever do more than one or two of these a week...

In the end, I'm not gaining any hours per se, but the hours I get are hours where I'm more productive (the alternative for me was taking e.g. 8pm to 11pm on evenings where I'd still be tired and generally wouldn't concentrate well at all). The structure of a nap, slowly easing into it, and then focusing totally while the house is entirely quiet works very well for me. Probably isn't healthy in the long term, though. But I need me time desperately to stay sane (got a 3 year old that otherwise occupies all my time at home when he is awake).

It's a massive hassle just to get that extra block of concentrated time (now, if I could afford to slack off the entire following day at work, it'd be a lot easier :) ), but it feels worth it at the moment. When my son gets older and demands less of my time so I get more time to myself earlier in the evening, I very much doubt I'll keep this up (though I've grown attached to taking 1-3 hour naps in the evening and working a bit into the nap instead, so that I'll probably keep up to some extent)