This is the most often asked question in panel discussions of
     polyamory, making some polyfolk wonder why sex is more
     interesting than the emotional and other intimacies of
     polyamorous life.  The answer is that the people involved decide,
     and they decide *how* they decide, too.  Some people have
     conferences and divide up the week, some people all pile happily
     into one big bed, and for all I know some people spin a big wheel
     with blinking lights on it each evening....and some people can
     love one another, have no sex, and choose to live in separate
     homes if that is most comfortable for them. The answer usually
     evolves out of discussion, empathy and practice, which makes it a
     lot like good lovemaking.

     As jack says:

     "The thing to remember is that the sexuality of a relationship is
     not the most important aspect of it.  The best thing I can do for
     either of my partners is meet them at the door with a buttered
     biscuit and a smile."