On sleep - I think it will be one of the biggest unknown variables that you don't know how you'll be able to handle it, until you experience it for yourself. Typically this will happen somewhere within the last 6 hours of those 24 hours - whether you can keep going, or find yourself nodding off and needing to make stops for naps. While you can't necessarily prepare for it, but being aware of the possibility that it may or may not be an issue will go a long way towards completing those 24 hours successfully.