Can you leave this in the drain longer than 8 Hours? 3 days, for example?? Any maximum amount of time? Thanks

Thanks for asking. When following label directions, this isn't intended to be left in your drain because you're either briefly running water through the drain or flushing it through the drain. However, it is important not to run water for 6-8 hours after following the directions. Leaving it longer does not mean it is more effective. – Brooklyn, SC Johnson Consumer Care