Keeping hand at heart level doesn't have relation to healing in that way..
The ultimate aim is to keep the limb elevated to prevent swelling at the fracture site..
The usual duration for fracture healing is 6 to 8 weeks. That will remain the same in either position.
The only difference will be that if swelling persists, it may cause pain..
Next Steps
You can do elbow movements intermittently. That won't cause any problem.. Also, continue active finger movements..