That's awfully sad if it ever gets so old that it's not enjoyable anymore. I hope that doesn't happen to me...
ANH is my favorite. The acting and writing is worse, but as a whole it is so well put together. But next time I watch them I'll re-analyze them and have a new favorite. That's the way it goes.
if you can manage, try to go two or three years without watching them. It really breathes new life into the trilogy for you.