On a related note, regarding VNAV path construction, aside from speed brakes, flaps or gear, the only other way to reduce airspeed during the deceleration phase is to reduce the descent rate. I think the original poster's question -- whether you are expected to add flaps near the maximum flap extend speed to decelerate and stay on the path, or reduce descent rate until close to minimum flap maneuver speed -- can be asked in a different way:
How does the FMC deal with the deceleration "knees," which must be calculated in advance and inserted into the predicted overall idle descent path? I noticed the vertical deviation indicator stays centered while the vertical speed decreases to about 500 fpm during the deceleration segment. Obviously, the path itself is not a constant gradient if you can change vertical speed from 2400 fpm to 500 fpm while decelerating (aproaching 10,000' or some other speed restriction point) and continue to stay on the path. I suppose you can keep the 2400 fpm descent rate going and decelerate if you add flaps just as you get below each max flap placard speed, but this is usually not what is preferred.
There must be some target speed that the FMC is anticipating for these deceleration segments. Is it the minimum flap maneuver speeds, maximum flap placard speed, or some speed in between?