You have the potential of earning more money with videos that are longer than 10 minutes vs shorter than 10 minutes as videos longer than 10 minutes gives you the option to place ads mid-video, however just by making the video longer does not automatically mean you will end up receiving more money from it as that is determined by ad impressions which is ultimately determined by a large number of factors including audience location, playback device, number of views, watch time, etc...