I have never opted for an assignment service and yes it helped my grades out of an unfathomable pool of stresses. My consultation assisted me a lot in doing my projects all well and duly on time. As far as your inquiry is concerned, "how long should literature review be?" The complete scope of the research and the threshold that the task sets determines the length and extent of a literature review. Generally, you should aim to write 1-1.5k words though be sure to ask your associate about the right word limit.