I have to say that that is one of the irritating things about elves (apart from the impossible elegance, skill, beauty, immortality things) is that in addition to all those things they generally have the instinct to know who the right person is for them and generally get it right .... obviously since they are stuck with each other for ever it is a good thing but..... for already lesser mortals, it is a bit galling.
So maybe since they "know"and they also have fixed boundaries... they are relaxed - though I wonder whether things would have been the same if Celebrian were around - daughters tend to be good at winding daddy and granny round their little fingers...