I level pretty fast in MapleStory, based on the difficulty of my class early on and being reasonably new to the game. Leveling is solely based on how well you spend your time while having fun.
My friend is CONSTANTLY online, and is only level 40. This is because he spends all his time in Henesys talking with newbies and bragging about how great Assassins are. Meanwhile, I’m talking in buddy chat, but at the same time, I’m at a Zombies map getting EXP. This is how leveling is achieved.