To be honest I never realised that the iBook G3 ran for so long, I was referring to the fact that it was released in 1999 and was surprised to find out that it was still available up to 2003, so I apologise for my inaccuracy there.
Regarding the NVIDIA chips, I was under the impression that Apple were replacing these for free anyway.
As for the failure rates, of course we don't know the exact figures (Only Apple will have this information). As I could find little information, I used statistics from a Gartner survey of computers covering the period 2005-07 (Whether this is any more accurate than pulling them out of the toilet may be debatable, I don't know, I'll leave that for you to decide).
PC Failure Rates Drop, But Not Far Enough, WebTechGeek.com
(I did find a more detailed copy but the server is down atm for that page)
As I was specifically talking about the iMac, I used the desktop figures. Their findings were 5% failure in the first year rising to 12% after 4 years. So basically 7% occurred during the 2nd and 4th years.
This survey covers all PC vendors and I (Rightly or wrongly, partly due to my own experiences over the past 12 years) presumed that Apple would be towards the higher end of quality in this group, plus the fact that the 4th year is not covered by Applecare anyway, so I shoved my hand down the u-bend and plucked out 5%
(As I would presume that a considerable chunk of the 7% would be in the 4th year, I thought I was being rather conservative with this figure).
PS
Toilets?, iBook G3s? Have I not heard a connection before somewhere?