These can be tweaked for shorter gameplay segments, but if you have the time I would recommend the «25 %» race length as a minimum. (playstationing.com)
With four different classes and race lengths varying from 1 hour 40 minutes right up to 24 hours, there really is something for everyone. (wtf1.com)
Race setups are equally as customisable and players have the option to set race length from 15 % (usually three or four laps) all the way up to 100 % (usually over twenty). (thevitalounge.net)