if i'm too tired to continue, i try and build the biggest stack i can. pop that money bubble, run my clock down until i sit out, and go to sleep. unless i just have a commanding chip lead and the final table isn't too far away, then i'll likely play. maybe i'll sneak in a power nap if i can afford it.
otherwise, i just take my min-cash and whatever money jumps i make and don't worry about it. a few times, i've made it pretty deep just sitting out. i think 8/9 once, which was nice.