It all depends I think is the correct answer. At EGNT they sometimes sit 'idle' overnight at the beginning and end of summer season and indeed often during the winter, but a few years ago I remember a JMC 757 getting delayed, and a 2nd having to be brought in to help it make up time, as they litterally had NO extra downtime AT ALL to enable them to ever catch the delay up!
Busy old world at times is the charter industry!
GWK