My 4.5GHz overclock on 2600K has become unstable!

It's been a while since I tested for stability of my CPU's 4.5GHz overclock. I ran the blend test of Prime95 of more than 6hrs back then and I felt that was sufficient. However, PC has been giving random lockups in the past couple of months and I didn't want to accept that the reason for this instability was because my overclock wasn't stable enough. For some reason, it was so hard to find the settings that made my PC stable, and I didn’t want to go through all that again. It could be because I wanted to both overclock and save power at the same time. That's not something that's easy to achieve, obviously. Or it could be because the motherboard is not the best when it comes to overclocking. Or it can even be that this CPU is a bad clocker. Or I could have been doing something wrong in the first place.

Anyways, the reason for the recent instability could be due to many reasons. The first one could be because the last time I checked for stability, I didn't use a version of Prime95 that supported AVX instructions. Then, I did a couple of UEFI updates and maybe I needed to change “some values” to make the CPU stable under the firmware that I'm using currently. Or it could well be a problem with the power supply or motherboard or memory.