Here's my 2 bits worth. 180 ESI systems installed so far (since 1999)- 5 hard drive replacements, 1 Compact flash replacement not counting the Samsung recall (all save 1 replaced before anything went wrong). I've gone through 3 hard drives on my office PC's in the last 10 years so I think 5 is not out of line at all. I expect it to become a regular thing soon though as those hard drives out there hit the 10 year mark.
