Is There a way that i can prevent my ps3 controller from shutting off?

May be...

Im trying to get "the peterson" trophy for fifa 09 which means i have to play 50 hours. I read that if i go into a shootout & leave the controllers alone it will work. I tried this but my ps3 controllers shut off. Is there a way that allows me to keep them on all the time?

yes, there is an option for controller shut off time in the system options, or maybe accessory options, look around, i don't remember exactly where it is... but make sure you plug in your controller so it doesn't die, and make sure you pay your electric bill, lol...

Maybe put a book onto a button?