My dogs are getting older.  My Shepherd is having trouble climbing onto the sofa.  He relaxes and feels good.  It's nice to see him comfortable. 
His body doesn't look like it's jumping because of laying on the hard floor.  Many times people think it's due to a dream but often they're laying on a nerve. 
He and my other dog love the larger size. Even though my smaller can fit in the smaller she thinks she is bigger so she kicks out my shepherd who is twice her size. 
Just know your dog's.