The style of the stories evolved over the years. For the first decade, the stories tended to be complete episodes. This was also a development period in which the author established his style. During the 1920s, the format gradually changed to serials; this was also a period of character development in which many of the large cast of characters were given their own storylines in turn. Many commentators agree that the "golden age" of Greyfriars stories was in the period 1930 to 1934, when the standard of plotlines and mellow humour reached its peak; while after 1934, the high standard of plot construction continued, but plots and themes were increasingly repeated.