I would say you are worrying far too much over longevity of your system. That sempron I have listed way up there I finally retired over winter break. It didnāt die, it was just so outdated I couldnāt play new games on it anymore so I upgraded to a quad core phenom. So I got 5 years 05-10 out of it and it was still going strong with a 33% overclock on cheap components. I didnāt even get better cooling. It was all on the stock heatsink with a bigger fan put on it.
Clock your machine as far as it can go while staying stable no matter what. Then check the temps under max load, if theyāre within safe operating ranges youāre good to go and never have to mess with it again.
Donāt use overclocking software, go through the bios there are more and better settings there, and youāre less likely to get data corruption from the computer becoming unstable while working with the harddisk since youāre not using the harddisk at all during BIOS. You will need some software for testing. I used CPUZ to see what my current settings were, and Folding at Home as a benchmark and stability testing(my sempron also ran this 24/7 for the five years of its life)