well, I know when you are not on a chat or not on a game your PS3 disconnect the headset,,,, some headset allow the auto turn on, which is good for the PS3, and some doesn't,,,, maybe thats the problem you have,,,,,,
now if its I advice you to get Motorola's headset, they have the best,,,, if its not then please let me know and I will see what I can find about this problem,,,,,