I take it out as soon as I can't mash it down anymore. however, when I cook smelly stuff like fish or other seafood, I NEVER throw the packages in the garbage. this rule applies to pretty much any meat product, cuz they smell up the trash. I usually run that stuff out to the garbage can seperately the same day.
also, i HATE is when folks try to a big item like an empty milk carton in the garbage. those don't even flatten out and they take up too much room.