In reply to confusicating:
i keep a fairly strict evening timeline, then cut into the morning instead. it may just be me, but i get more done by getting up early having rested properly than burning on late.
i usually finish at a time that allows for enough rest, proper eating and downtime, which makes 4am starts etc no big deal (i admit coffee has a lot to do with this equation).
when early starts happen i just move everything forward, lunch at 9am etc, and think of anything after about 3pm as going into extra time. its worth noting that 3pm is still a reasonable time to imbibe caffeine without too much effect on sleep if things do go late.
its gotta be the end of the f*cking world for me to be working on something im not naturally inspired by after 4pm.
the worst scenario i can think of is going so late you need booze to put you to sleep. somethings blown a fuse there. chemicals to start you up i believe is healthier than those to send you down.
wont work for everyone tho.