I really don't think sex gets boring after a few hours, if you pace it right. My girlfriend and I once went for 24 hours straight. It was not exactly 24 hours of just banging away. We took a lot of breaks to eat and take showers. We stayed naked the whole time, in and out of bed. We kept the interest going by having sex in different positions, and in different parts of the house. We did it in the bathroom, in the livingroom, on chairs, and funiture, and on the couch, and we had sex outside in a fenced off area. We also did hours of foreplay, alternating with hours of non-stop banging. I lost count of the number orgasms we had, but I think she had twice as many as I did. We have had a number of long sessions since, but we have never equaled that one night. It was fantastic!