If you are concerned with the temperatures and want to reduce them elevation of the rear of the machine helps, as sitting flat on the desk only reflects the head back to the base of the Mac. You can buy passive aluminium coolers like Rain Designs Mstand or iLap. Most powered coolers are designed for PC notebooks and dont work overly well with Mac`s one cooler that does work efficiently is the Moshi Zefyr 2, as it`s principle of cooling is specifically designed for Apple portables, by blowing the air horizontally across the base of the computer, however don't expect miracles.
Link:
Moshi Zefyr 2
You can use software to override Apple`s own cooling algorithm by manually taking control of fan RPM and setting up power profile presets with SMC Fan Control (needs update for 2012, temp sensor presently not recognised), or you can look at
UltraFan which allows you stipulate a preset temperature and the software will automatically raise and lower fan RPM`s to keep the system at the predefined temp, which i personally feel is a far more elegant solution, at the end of the day you want to control your system temperature, and not your fan rpm`s.
Strictly speaking Apple`s own cooling algorithm works, albeit at sacrifice of increased temps for quieter operation, this has always been the Apple way and is really nothing detrimental to the systems, i have one MBP from 2008 all original barring a recent fan change that has an uptime of over 30K hours. The latest MBP`s need less assistance in remaining cool; for some it`s simply disconcerting the heat generated and transferred to the case, although it`s perfectly normal as the aluminium acts as a heat-sync. i have to deal with elevated ambient temperature so at times a software solution is useful. Apart from the passive cooling the Mstands bring they also offer a very sound ergonomic solution.
High temperature in general is not overly harmful to your systems, what is far more detrimental is thermal stress, when temperatures rapidly fluctuate by significant margins over a short period of time. Anyone striving for longevity should look to minimise rapid fluctuation of temperature.
The old adage still applies; it`s easier to keep a system cool, than cool-down an already hot machine. This being said it`s not strictly necessary, equally it`s nice to know that there are options for reducing temperature.
