bath robes are too constricting for laying on a couch, and not that comfortable all things considered. Further, my bath robes at least are short sleeved.
When it's cold I sleep in my bathrobe (we call it a "dressing gown" which is a particularly poor name for it as one wears it when not getting dressed!). It has long sleeves, is below the knee in length and snug - very comfortable.
