Today we went to Temple

The battery in a 3 and 1/2 year old Mac Air suddenly failed last week. We took it in and said that we felt that it was reasonable that a battery on a Mac Air, a premium lap-top after all, would last longer than 3 and 1/2 years under consumer law, the Genius' disagreed. They felt that it could have been replaced under consumer law up until about 3 years of age.
I guess it is handy to note that when you are looking to buy a premium laptop from Apple that one can only assume from the information provided today that it is not reasonable to expect an Apple computer to last more than 3 years.
Or, have I got that wrong?