Decanting allows a wine to be exposed to a large surface area of Oxygen. This is done to help the wine show its true potential, by mellowing the wine and allowing it to express hidden aromas. A well made wine will always benefit from an hour decanting. A wine that was closed and not up to much when first opened should be jumping out the glass ... unless it needs more time in the decanter or is rubbish to begin with. This isn't much help is it? Ok rule of thumb, if a wine has enticing aromas, but is somewhat elusive, give it some time.
So why so serious, or why are you banging on about this decanting so much? Well if you have stuck with me this far I will tell you why. I opened up the bottle over to the left on Saturday night and had two glasses. The wine displayed nice tight aromas of red fruits and nutmeg. Still slightly closed i left it with trusty Mr. Roboto.