How long to leave a body undisturbed after death?
The site urbandharma.org mentions that the body should be kept for about 3 days.


  Immediately following signs of physical death, Buddhists believe that it is best to keep the body in a peaceful state. Traditionally, the body is taken to the home and for a period of 3 days or so, the body is not touched and extensive prayers are said. This facilitates the process of the person’s consciousness letting go of its prior body and life and all of its attachments and more easily moving to the next.


http://www.urbandharma.org/udharma8/health.html

The exact number of days may vary from tradition to tradition.