cream puff you say
True. It's also true that any manufacturer of any product occasionally has quality control problems and produces bad batches
Sorry this is totally incorrect.
Aircraft servicing is a preventative engineering process. This means we repair replace etc before it breaks or fails. Hence a in this instance we change plugs a the manufacture's recommendation's and have the magneto serviced at the 500 hrly inspection period as per manufactures service period instuctions.
If there is a bad batch then this is taken up else where, ie SB, MSB. AD etc etc