Back in 2006, there was a short presentation given by Captain Mike Bryan of Boeing at their operators' symposium, in which he argued for removing the recommendation against manual flight with the autothrottle engaged from the FCTM. He cited a number of advantages, including no longer needing a speed additive due to winds, fuel savings, reduced workload, etc. As I don't have a current FCTM, I don't know what Boeing has actually done. However, my operator's standard policy is to keep the autothrottles engaged throughout the entire flight. Obviously, this is a requirement for a HUD CAT III landing, as we fly those approaches with the autopilot disengaged from the final approach fix to landing, while keeping the autothrottles engaged. In any other case, our US Op Specs require the autopilot to be disengaged by 50 feet below the MDA, and never lower than 50 feet RA. We are not trained nor authorized to use the autoland feature, thus we never engage two autopilots at the same time.
That said, one of Captain Bryan's cited disadvantages to a new policy was pilot proficiency with manual throttles. Sure enough, about 3 months after I got on the airplane, I picked up a ship with the autothrottles deferred. Having crossed the ocean dozens of times before autothrottles, and several times since with them deferred, I thought no big deal. Next thing I knew we had levelled off at 7000 feet and the wind noise was winding up as we passed 290 knots. Now I generally disconnect the autothrottles for all visual approaches, as we always did in previous airplanes, just to keep engaged with throttle use. Funny how quickly we become complacent, as smart as we think we are.