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.