My Book Essential 3TB Life Span?

I have connected my Digital Book 3TB Essential External Drive to My WD LIve hub Tv through USB.

I am using the external drive for 3-4 hours a day max,  for videos and music, and i was wondering what could be the life span aproximately of my external hard drive? Most of the people say  its about 5 years. 

a week to a few years if you are lucky.

A hard drive life span could be from 3 to 5 years.