Two years is the right number.

Between the advances in technology, weight, size, and the boredom factor, two years is long enough to go without a new toy.

And importantly, there's a bell curve on the aftermarket value of the notebook when you want to sell it, anything over two years old deflates dramatically. Let's say you had a $1000 notebook when new, to sell it at the two year anniversary you might get $700 for it whereas if you go to three or four years it might be worth $200. Selling at year two would make you more money than keeping it and selling it at year five, you would needlessly have suffered in an old notebook for a few years for no financial reason.

BJ