[schettj]

Using the built in internet connection sharing over USB, with backlight off, keyboard open (for cooling) and nothing else running on the TP is your best bet. If your lappy is kind and has USB2.0/1A usb power, you should be able to keep even until/unless it overheats and stops charging.

Pretty much heat is the enemy. Anything you can do to keep heat down is good. Propping it up so air can get under/around it, sticking it in front of a small fan, or the fridge (not really - no signal in there) or on top of your AC, or outside in the winter - all that would help.