A system and method for scheduling advertisements in a television service network environment. An ad scheduler prepares an ad insertion schedule based on channel change statistical information and avail time information. The scheduler evaluates the statistical information, time durations between adjacent avails in a presentation stream, and the relatedness of market segments assigned to a plurality of advertisements. It schedules the ads into presentation stream groups based on this evaluation. The statistical ad scheduling allows the system to eliminate “forced” switching between multiple presentation streams, whereby system wears and malfunctions can be decreased.