More than you would expect. With hangout gaming, you don't have side conversations and other distractions that disrupt the flow of a game. Players tend to have better attendance, and I rarely have to cancel, so we often end up getting in as much or more session time than if I were trying to run something with longer sessions. In my case, it has also allowed me to run five different online games at a time (four per week, with two games alternating biweekly).