The wonderful thing about art is that it is always new. This is because a work of art is not merely the sculpture in marble, the print on paper, the notes on the staff; the truth and essence of it is in the interaction between the artist and the audience. And while seeing something for the first time is perhaps the strongest experience one can have with it, with a really good work one can appreciate new nuances and a fuller flavour over years and years of familiarity. Perhaps the trick of it is simply to see it for the first time every time you look at it.
Mike Johnston, as usual, says it better than I can.