[Beowulf] Cooling vs HW replacement

[Ariel Sabiguero]

Hello all.
The following question shall only consider costs, not uptime or 
reliability of the solution.
I need to balance costs of hardware replacement after failures over air 
conditioning costs.
The question arises as most current hardware comes with 3 or more years 
of warranty. During that period of time Moore twofolded twice hardware 
performance... is it worth spending money cooling down a cluster or just 
rebuilding it after it "burns out" (and is at least 4 times slower than 
state-of-the art)?
Is it worth cooling down the room to a Class A Computer room standard or 
save the money for hardware upgrade after three years? In warm countries 
keeping 18ºC the air inside a room (PC-heated) when outside temperature 
is 30ºC average it becomes pretty expensive to pay electricity bills. It 
is cheaper to "circulate" 30ºC air and have from 40-50ºC inside the chassis.

Do you have figures or graphs plotting MTBF vs temperature for main 
system components (memory, CPU, mainboard, HDD) ?
Links to this information are highly appreciated!
I remember old (40MB RLL disks shipping this information with the 
device, several pages of  printed manual) hardware showing the 
difference in MTBF vs environment conditions, but nowadays commodity 
harware does not consider this on the sticker on the top of the device...

Regards

Ariel

PS: if the idea is worth the money, then I would like to study 
reliability and uptime, but it is not the main concern now.