6.3.19 HDD Life  As stated above, a life of 40,000 hours is estimated for many commercially available HDDs. Typical commercial use of HDDs would give these disks a replacement life of five years. With improvements such as fluid/ceramic spindle bearings, surface lubrication of disks, and special head parking techniques made on the most recent desktop HDDs, the life of HDDs may be somewhat longer. However, there is no reliable testing of the life span of unused HDD and it would be astute to plan to replace the disks in such a working system within 5 years.