If you're always rested, and gain more XP per kill, you logically level faster than someone who isn't. It takes longer "real life time" as you're spending more time resting.

So while someone who played none-stop (no sleeping etc) could hit 70 in 1 week (RL time) or 7 days /played, someone constantly resting can only level up 1.5 levels each 5 days (max rested is 150%, which takes 120hrs to accumulate). It would take them a heck of alot longer, but they'd have a lower /played time by 70