I was starting to doubt that it was ever going to happen, but this morning I hit level 20 in the leadership profession on my cleric. Based on the amount of Ardent Coins I've accumulated, this took me 239 days. On most of these I just logged in once in the morning to invoke and re-queue my professions. Admittedly I probably could have halved that time by doing this twice a day. Speeding things up any more than that would have been difficult however - at least without real money entering the equation - considering that most of the good missions take 8-12 hours. All I can say is: that's one hell of a time gate.