I just listened to the Gardiner 'Eroica' and I must admit that it is a remarkable performance. I read some of Gardiner's comments online about the symphonies concerning authoritative sources and Beethoven's own markings and notes and the fact that throughout history, most of these documents were overlooked or ignored. I want to add also that most of the musicians available during Beethoven's lifetime were inconsistent when it came to their levels of technique and musicianship and that additional instrumentalists could be added to or taken away from a performance based on a performers ability. Adding in parts was often an undertaking that was done by the orchestra director. So, the hard and fast rules that we observe today were not really understood in either the 18th or the 19th century.