20 days /played for level 60.
mid 30's through mid 40's I started to get bored, logged in and just sat around doing nothing for hours, etc.  very, very unmotivated/lack of anything really to do.  Helped out a lot of friends around this range.  Gained interested when I got close to 40 (mount!) lost it quickly afterwards.
Levels 52 -> 60 I did in a week (about a level per real life day).  
Its all about goals... wanted to get 53 for devilsaur gauntlets.  Ground to 55 for devilsaur legs (Hippogriffs in azshara gave me a level in roughly 9-12 hours played).  Straight questing from 55 -> 60.  Straight.  No grinding.  Did all of western/eastern plaguelands/un'goro/felwood/burning steppes during this time.  59 -> 60 I did in a day as well ... Had saved all the winterspring quests for this level.  59 -> 60 were done SOLELY in winterspring.  ~14 hours if I remember correctly.  Possibly slightly less. 
Unlike some of the people here, I found the post-50 levels to be the fastest ones besides the initial 1-20.  Much, much faster than the mid 30's through mid 40's.
I'm on a pvp server as well so ... account for lots of raiding time/ganking time -_-
Edit: Didn't step into end-game instances until level 60.  Bad idea for leveling ... raid groups = about 12xp per mob.