This is a good reason to look for a seller with a good return policy - 30 days minimum IMO, or 90 days even better (Target, Sears, KMart, Walmart, Sams, Costco). HH Gregg usually has the best prices but have only a 15 day return policy. Still, most dead pixels will show up by then as they are a manufacturing defect that should not have passed QC.
For the record, I still use a 5 year old 42" Panny ED that to this day has no problem pixels and no problems period. Purchased at Sams Club. It was made in Japan, which may explain that. OTOH, my brother has a 4 year old 50" 720p model, made in Mexico, and it also has had no problems including no bad pixels. His was purchased at Rex, which closed their local store last year.