Well of our current batch of HP's only one has a problem, smashed screen, because it was droped on a concreate floor
However that is not the best indication of the life span of a laptop, ie there is no way you can tell if a new model will last or not, only time will tell.
So we have to base our choises on past experence.
On the subject of dell's roughtly 2 years ago we go 16 dells, and another 16 3months later
The 2nd set were a new "improved" model which replaced the original ones.
So far we've had to call out the engineer for every one of the new "improved" models, but not one of the older models.
The speed at which companies are changeing laptop models these days is makeing it far harder to guess/predict what is going to last and what is going to be a fault ridden flawed design.
I would not exepect any laptop to fail in the first year, however after 3 years thing get far more shakey