There seems to be a slight misconception here about lowering the gear.
You don't normally lower the gear to get the speed down; but you (might) lower the gear to increase the rate of descent in Emerg Descent. I emphasise 'might'.
At low altitude (arriving for landing, say) you might lower the gear earlier than planned if you are a bit high on speed - there was a reference earlier to using gear as airbrakes.
Quite different situations.