Mortal Moxie from immortal machines was lucky enough to talk with Battlefield Heroes' Lead Designer, James Salt and Art Director, Gustav Tilleby. Here's a snippet:
"Mortal Moxie: How does character development work, and how long can players expect to 'grow' their characters before maxing out.
James Salt: Character development in Heroes is a lot like you would find in an MMO. You increase your characters experience level by damaging enemies in the game, to gain experience points. Once you reach enough experience points, your Hero advances to the next experience level. As your Hero levels-up you gain access to different weapons and clothing customization items in the store. For each round of Heroes you play you gain in-game currency to spend in store.
We expect it to take around 80 hours to reach the current level cap. However we will be regularly adding new updates to the game, this will include raising the level cap occasionally."