The OP is nice. They did have some hints in the earlier seasons, I mean the talk in the hospital when ben was born, the flashback episode when he gives her a hug in the towel, and alot of moments when they just looked like a couple. Quite a few times looking cuddlie and close on the CP sofa. I think they probley always thought of the option and finally went with it in season 5. I am so glad they didn't just do a one time deal, or london deal. I am so glad a relationship grew out of it.