Cooling is something you actually need when you overclock your raspberry or when it will operate in high temperatures. The following article describes a way of overclocking and cooling the raspberry Pi.
http://stadar.org/content/raspberry-pi- ... nd-cooling
you made a typo!
your "or" should be "and"
If you overclock and
operate the PI in a hot environment, only then it will make any sense to try to cool the PI, but only passively (small heatsink) and only on the SoC. Overclocking has no effect on the LAN9512, and all that it does is making it more unlikely that the PI will shuttle back the overclocking when it becomes hotter than 85 degrees Celcius.
other measures are not financially sound, as even in extreme cases the PI will only last a half year shorter than its expected lifespan, (estimated at at least ten years).