For example, published time for replacing rear shocks on Nissan Titan could be as low as 0.4 hr (24 minutes) or as high as 1.1 hr (1 hour 6 minutes). Where even these times came from and why they are so different – it seems like no one knows! In fact actual time to do this depends on your tooling, equipment and condition of the vehicle and parts involved in this job. Also, to a small extent, it depends on the mechanic’s experience. With equipment just right for this particular job, clean parts and couple of previous attempts to find an optimum way to perform this task, those shocks could be actually replaced in 5 minutes :-).
differ greatly from one book to another