You can leave whenever you want. Typically you should stay for dinner, cutting the cake, and to say congrats to the couple.
I was at a wedding recently and the bride/groom "left" for the pictures and for the grandparents to see. They went back in and some people left while others went back in for more of the dancing and festivities.
I was at a wedding recently and the bride/groom "left" for the pictures and for the grandparents to see. They went back in and some people left while others went back in for more of the dancing and festivities.