I am curious about two things here. To the OP, and you putting your receiver into the standby mode when not watching it? Second thing, are you running your towers as full range?

If you are putting your receiver into the standby mode when not watching movies or listening to music, I would suggest you turn the receiver all the way off. If you are running your towers full range, and listening to a movie like Saving Private Ryan beach scene at high levels, then expect your receiver to shut down during the loud passages - as this scene is challenging for any system when played back at high levels. If you are going to play this movie at high volume, I would suggest putting the towers and all of the other speakers on small as well, it will reduce the load on the main channels, and can prevent the receiver from shutting itself off. Does this receiver run hot before shutting itself off?