A few weeks back I had posted some renders of Hellborn's ocean waves- (which I don't have handy at the moment)- but I stretched his Procedural wave set, which was just a small chunk- and made it cover an approximate 50 square miles of open ocean... The end result was a giantic ocean of waves all the way to an endless horizon- all made from a small Procedural wave chunk- so that's what you can do with a Procedural Terrain- expand it endlessly (in theory anyway). Of course, it doesn't need to be "endless"- it only needs to cover the camera's field of view...