6months is ok la.
Mayb the cooling isnt enough. Its still a lot better than those with XPS1530 that keep having dead mobo after 1-2months.

Depends. If say my unit is new (1month old or so), I would argue with the customer service. Definately have a case against them. Afterall, even though they provide good after sales services, but not all people really fancy ripping their new toy apart. Moreover, you dont know how long the replacement can last if a new one can die within one month.