i would suggest, good ventilation, my 4 harddisks stacked side by side almost 4 years without issue. tempreture keep between 35 to 48 should be ok ... my on load harddisk tempreture is about 48 when i playing game and stuff.

even when im torrenting ... the tempreture is around 42 only.

also another important thing is the voltage. make sure your PSU has enoght power to supply to your all your harddisk. or else your harddisk start up will have ...vrrrrrr...tek... vrrrrrr...tek.......

my PC start up on 120GB sata1 is like only 20 sen ... without any issue.

just make sure on that lar... i believe harddisk dont die so easily... no big bumb or drop... it should last for more then 6 years .

my PC spec

Enlight 450W PSU
Intel 3.0EGhz
2GB Value Ram
2x 120 GB (sata)
1x 320 GB (Pata)
1x 250 GB (sata)
1x 320 GB (USB)
Nvidia 6600GT AGP
1 CDRW and 1 DVDRW