The design to turn it off after a short time is to avoid problems with panels and image retention. I can send this up as a suggestion for future firmware updates, but I wouldn't be aware of that being implemented unless it's released.
Instead of pressing pause, try pressing STOP, and then when you come back, hit PLAY. It may work with some file formats, but just a suggestion.
I have just bought a Samsung BD-P1580 which is a fine machine, and have successfully updated it to the latest firmware. The only problem I have is that when I play Divx movies using the USB interface with either a USB stick or hard drive, and pause the movie, after two minutes or so the machine switches to STOP and loses the place in the movie. This does not happen with DVD or Blu-Ray discs, where the pause control lasts indefinitely. Is this a problem with the spec which could be solved through a firmware upgrade, or just with my machine?