Orientation of PC during burn-in?

I heard a rumor that when you build a new PC, you are supposed to "burn" it in for about 24 hours so the thermal paste will correctly bond between the heatsink and the CPU. Assuming this is really necessary, does it make any difference if the CPU is orientated horizontally or vertically during the burn in process?

It would seem to me that keeping my CPU horizontal during the burn-in would allow for the most even distribution of the thermal grease bond. On the other hand, once I am done with the burn in, my CPU will be orientated vertically for all future use.

Solution 1:

The is no technical need to burn in a new computer or new hardware.
Nor will the thermal paste bond with the CPU or the heat sink. The cooling is done by passing heat between the CPU metal and the polished heat sinks metal and the heat transfer of this is significantly higher than if you use thermal paste to conduct the heat. What thermal paste is used for is to fill the very small unequal parts in the metal (even after polishing), allowing more heat to be conducted. This is why you use a grain sides dot of paste and why cooling degrades of you use to much.

However it does make sense to test your new configuration.
See if it still works when it heats up. Try it for a few hours (not necessary all continuous hours). This is not a burn in. Nothing actually changes. Your computer will not behave if differently if you do or do not burn in.