If it took me six months to become productive, I would be deeply embarrassed. There must be something wrong with the talent pool you are able to attract.
To elaborate a good engineer will be able to read a well designed system and almost immediately start mimicking what needs to be done when adding new features regardless of how much experience they have in the given language/framework.
To elaborate a good engineer will be able to read a well designed system and almost immediately start mimicking what needs to be done when adding new features regardless of how much experience they have in the given language/framework.