Firefox _never_ crashes for me because of Flash since I started always using nspluginwrapper. All that happens at most is the Flash plugin process dies (npviewer.bin). I can also just killall npviewer.bin anytime I want to killall Flash processes. I'm telling everyone!
My sleep timer (for long running Flash streams)
# wait 1 hour kill flash turn off LCD
sleep 3600; killall npviewer.bin; xset dpms force standby
My sleep timer (for long running Flash streams)