I have had about 6 laptops since 1994. They included SoundBook, WinBook, Gateway, HP, and now, Lenovo. I have toted these puppies all over the world. My usual practice is to get a new one when new technology warrants. I give the older ones to my kids, and one has even passed to the grandkid level.
Eventually, they all wear out. The older ones lost their floppies, and CD drives, and batteries had to be replaced.
The two that have endured and are as good as new are the HP dv1000 and the Lenovo T60. I will probably replace the Lenovo next year with probably the successor to the T400.
The Lenovo is a tough beast and very reliable. Mine fell off an airport security counter and fell 3 feet to a concrete floor. No damage at all. (Since then I keep it in a neoprene sleeve when travelling.)
Like all things, durability greatly depends on how you take care of them. All things being equal, I will go with Lenovo.