It is well known...

To every house dog that the best, most comfy spot on the couch is the nice pre-warmed spot recently vacated by a human.... I've found it best to not wait for them to get all the way up... M is easily distracted and I've lost out on good body heat because of that.  So now when it looks like they are making a move to get up, I just go ahead and make a move of my own...