i suspect that the time it takes to goblinize would vary based on how extreme the goblinization process is for the person involved. Two weeks seems like an appropriate time for the bones to break and extend, muscle mass to develop very rapidly, calcium deposits to harden into dermal plates, etc. To go from a human to an elf would probably take a day, maybe two. Human to dwarf might be as extreme as human to troll, given the tremendous amount of bone damage that needs to be done.