What are the best power settings for me and my laptop?

I have a Acer Aspire 5551-4200 laptop. Right now I keep the battery in the fridge and run on the power cord full time. I don't give a hoot about saving energy. My only concern is what's best to preserve and prolong the life of my laptop and prevent damage to it from overheating. My previous laptop, a Dell, died from repeated and prolonged overheating, and I want to preserve this laptop as long as might be possible. I could configure the Power Options so it never turns the display off, never sleeps, and doesn't do anything when I close the lid, but that would eventually lead to overheating like it did on my Dell. On the Dell I had no choice because I didn't have a battery. The battery conked out after only about twelve or thirteen months. I keep this battery, a lithium ion, in cold storage at about a 40% charge when I'm not using it, because I want it to last. So I pretty much keep the Power Options on the factory defaults. The problem is that the darn thing cuts off or goes to sleep or whatever the heck it does while I'm trying to run a McAfee full virus scan, or charge my digital media player, or some such task that lasts more than a half hour or so. I'll set it to do one of the above or something similar and come back later and it'll be dark, and when I wake it back up the scan will have paused in progress, or the digital media player will have stopped charging, yadda-yadda-yadda. So does anyone ken my problem? Can anyone suggest the best Power Option settings so I can keep the darn thing awake long enough to finish what I thought I asked it to do and still have minimal long term detrimental effect on "my poor, poor bairns" motherboard.