Grand master is a title that is usually given to the head of an organization of a style, if that organization believes that is in its culture to call someone a grand master. Is not a matter of years, is a matter of that. Personally I don't think that in 2014 is something that is in the culture of most places., Here we call the president of a country by his first name and only, we are going to call a martial arts instructor grand master? Think about it:)

There is no ranking hierarchy in Wing Chun, since there are plenty of lineages around. The most popular lineage is the one of Yip Man, however, there so many sub-lineages (many students of him and many students of them, having their own) that is still the same case (many lineages). My advice is that you shouldn't care about martial arts politics but for martial arts training and the enjoyment that you get from it.

One of the secrets of Yip Man was that. He didn't care about those politics and so many of his students have created their own organizations by just making few small changes. So the famous Yip Man actually encouraged them to have their own small differences and interpretations according to what was better for them, making the art their own. That is how a martial art should be. An art, not a cult.:)

Grand Master is a term that is being more and more abused each day. Everyone believes that it takes something different to define one. Some martial arts at one time would only call the head of the style the Grand Master. Now many organizations are handing out the title as if many people deserve it. I know of some styles that have many Grand Masters, some as low as 7th dan.

...

all I know is what my Sifu has told us ..In shaolin it is used for the head of martial arts school.. but the head monk is the Abbot and he is the head of the whole temple.. the Abbot over sees every thing in the temple he is even the one that grants if you can train in martial arts... Grandmaster outside of shaolin is normally the founder of the art or head of the school. most the time when a teacher steps down the next in line gets this title.. but their are lots of grandmasters who are not real.. just like in china now not all shaolin monks are real abbots or monks they where put in by the government.. just like pugpaw2 has said it used very loosely now

Master that is Grand

What defines a practioner of say Wing Chun a Grand Master in the art? How many years of training would be expected of the individual? What is the current ranking hierarchy in Wing Chun?

Just answer what you know. Thanks!