Ignition Coil fail

Over the past 15 months I have had two ignition coils fail on my 2006 VE Commodore Omega, which has 93,000 km on the clock. The first was replaced under warranty; the second on cost me $336.15 to replace by the local Holden dealer. I have owned seven Holdens over the past 42 years and this is the first time that I have experienced ignition coil failures, and the local Holden dealer tells me that it is not a common problem with the VE. Are you aware of the problem? If not, is it possible that my vehicle has been fitted with 'lemon' coils, and if so do you think that it would be worth my while to approach Holden to have the remaining four coils replaced free of charge? It is a bit daunting not knowing if the remaining coils are likely to fail in the immediate future.