I have been rather lax regarding monitoring CPU and RAM temperatures, possibly because I have never had a failure there. However, I have had many hard disks fail over the years, before I took steps to install fans just for them. I now monitor their temperatures with Hard Disk Sentinel, and I make sure when I make hardware changes that I have fans in place to keep the disks cool (or at least coolish). I never let them get so hot that the tray display shows red.

It is now several years since I last had a disk problem. The last was when two 1.5 GB Seagate drives started reallocating blocks at about the same time into their short lives. I replaced them as a precaution but lost no data that I am aware of. I feel sure that the problem was a design issue rather than overheating.