When it come to anecdotes... I've got a powerbook and an ibook both still alive and kicking after close to 5 years and apart from the battery that I had to replace, they haven't had any problems (despite using them a lot)...

On the other hand my 2 years old macbook is starting to make some strange sound (the fan probably needs to be changed)...

I think that anecdotes are only that and in my experience once you have a problem with a laptop it's usually going to be more than one problem...