Basically Portable Hard Disk drives (or even internal ones) are complex electro-mechanical devices that can suffer performance degradation or failures due to a single event or a combination of events occurring over time. Environmental conditions that affect drive reliability include ambient temperature, cooling air flow rate, voltage, duty cycle, shock or vibration, and relative humidity. So the lifespan depends on all these factors. In general a portable hard disk can have a definite life span of 2 to 5 years and is liable to crash. They do not have a long life span like some of the recent backup devices like flash drives and thumb drives.

Answered by A.R.Karthick , an ibibo Master, at 9:04 AM on July 04, 2008

Because a portable hard disk is in an enclosure it gets hotter than when it is mounted in the pc. So it can decrease the lifespan. I bought a 500gb external drive and used it for backups and it died in 3 months

Answered by alok , an ibibo Advisor, at 10:41 PM on July 03, 2008