I found something of interest here: http://forums.whirlpool.net.au/forum-replies.cfm?t=2001999&p…
http://www.apple.com/environment/reports/
Search for "year":
Mac mini:
• Use: User power consumption assumes a four-year period.iPhone 4:
• Use: User power consumption assumes a three-year period.Mac Pro:
• Use: User power consumption assumes a four-year period.27 Inch Monitor:
• Use: User power consumption assumes a four-year period.So if Apple's eco projections assume a 3 or 4 year period it would be reasonable to say the device should last that long.
Thoughts?
Edit: Fixed link.
link doesn't work