That was 9to5 Mac. The poll now shows over 70% replace them every 3 years or longer. If you add the every 2 year group, you're well over 90%. Yearly upgraders are damn near statistically insignificant.
Furthermore, that 9to5 Mac poll was likely visited by Apple enthusiasts. The average consumer (non-9to5 Mac reader) will likely even skew the results more. Apple enthusiasts do not necessary represent the avg consumer.