Comment 6 for bug 958279

You can improve the situation by installing xautolock and xdotool. Using these two tools you can have the mouse move every x minutes of no activity. 5 days with no black screen of death!

e.g. run the following in a terminal window and the task is put in the background:
xautolock -time 1 -locker "xdotool mousemove 10 10" &