My previous car, a 2006 318i that had the same problems.
Whilst under warranty, BMW only replaced the faulty pack. Then a little later another coil pack will fail. Again BMW only replace what is faulty.
As soon as the car was out of warranty I went to the local independent BMW specialist and they told me that all four should be replaced. As when one of the pack fails it will spike the others, so another failure will be imminent.
They replaced all four for £141 inc parts, labour and VAT.
The problem never came back after that. I only wish BMW replaced all four in the first place. Probably would have saved them money in the long run and wasting my time.
I find it astonishing that both a 2006 and 2010 build (see my previous post) can both experience the same coil problems.
This appears to have been a major failing of the petrol engines covering a period of some years.
Quite disheartening really that the same problems are allowed to manifest themselves by BMW over a extended period.
This is my first BMW and most probably be my last.