Further to what Gold Leader said.....330 +knts approaching reversion mode sees you poorly placed if you also encounter turbulance in a descent and leads into a pilot overload situation best avoided.
A programmed M.78/290Kts and 250kts at and below 10,000agl is a Boeing manual approved fuel saving option and works well for turbulance and speed containment and achieves VNAV path at a more gentleman like speed and ride and gives you more thinking and monitoring time. Reduce the stress.