My first character to reach level 60 in World of Warcraft was my warrior, who needed 21 days of /played time for that. Which at the time was pretty much average. My second and third character to level to 60 were both priests, one Horde, one Alliance. Both of them needed 13 days of /played time to reach level 60. Today my mage reached level 60, my fourth character that got so high. But the mage only needed 6 days of /played to get there. Part of that is him being an alt and not being played all the time, so he often had rest xp bonus. But the major speed boost to level 60 came from patch 2.3, which decreased xp needed up to level 60, and increased xp for quests up to level 60.
Only cloud on the horizon is that fast leveling stops now. For level 61 I need nearly 3 times as many xp than I needed from 59 to 60.