I bought a prebuilt pc that had some screws missing from the fan and a cheap off brand psu so ive checked everything else in the pc but the heatsink. The cpu is an i7 7700k with a corsair h60 liquid cooler. Ive had the pc for about 5 months and daily have long gaming sessions. If they had forgot thermal paste would the cpu have fried already? I would check but ill have to go buy thermal paste to reapply and ive never applied thermal paste. I check temps from time to time, nothing crazy. The highest I remember is around 70 C under load.