http://www.amazon.com/dp/B004RMK5QG/?tag=satell01-20
It's $50 per year or they sell a 3 month option for $18. Keep in mind that this will be required for online play on PS4 so if you plan on getting one it might be worth it to just jump in now. For this fee you get auto updates at night and new "free" games every month. They call them free but you are paying $50 so in reality they are just really cheap but most of the games they give out are actually good and relatively recent releases.
For example some of the free full retail PS3 games this month are Uncharted 3, Saints Row the Third, XCOM, and Deus Ex: Human Revolution. If you are in to Indie games or own a PS Vita it's an even better deal. As of today there are 21 free games and you keep all of them as long as you are a member even once they are rotated out for new games.
You don't need to leave your PS3 on. This is how it works on PS3, this will all be irrelevant on PS4 because it will always be in a low power state to download new games and patches in the background. You pick your update time. I don't remember the default but mine is set for 4:00am. Every night at 4:00am my PS3 boots up and syncs all my trophies with PSN, syncs all my game saves with the cloud saves, downloads and installs all new game patches for every game I have played, downloads and installs anything new in my download queue, and downloads new system FW so it's ready and waiting for install when I boot up. People know about most of these features but most people never mention the cloud saves. If you have PS Plus and multiple systems or a system failure you can download all your game saves to any PS3. Yes it sucks to need a new system but at least you wouldn't have to lose your progress in all your games too. When it's done with all of this it shuts itself back down so you never even know it happened unless you happen to be awake in the middle of the night. You can set this update time so it works for you unlike my hopper.