My bad, I mistook the character transfer with the faction change service. Still, I remember there being a push for it which seems to be confirmed by the wiki: "

My bad, I mistook the character transfer with the faction change service. Still, I remember there being a push for it which seems to be confirmed by the wiki: "initially, there was a 6 month cooldown between character transfers. In late February 2008, the cooldown was reduced to 1 month. In July 2009, the cooldown was reduced to 3 days." Regarding heirlooms, they were introduced in WotLK: "Heirlooms that increase experience and scale based on character level were introduced in the Wrath of the Lich King expansion." The line is blurry, but I believe that a trend was definitely noticeable even in late Burning Crusade. In particular, efforts to attract a broader player base. It is unfortunately surprisingly hard to track and timestamp all the controversial changes introduced to the game.