Leaving A Tampon inside your Vagina for 12 hours or longer than 12 hours can cause an infection of your Vagina or in some cases Toxic Shock Syndrome.
Never leave the Tampon inside your Vagina longer than necessary to prevent Toxic Shock Syndrome or Infections and always remove the Tampon when no longer needed.
It's recommended to not wear Tampons longer than 8 hours which be both during the day and night.