Looking at the original situation from a different angle, is there anything wrong with asking ATC if 180 kts, or whatever your S speed is, is OK? They are well aware that we are trying to fly as efficiently as possible to avoid making too much noise or burning too much fuel. Don't ask, don't get?
Question for ATC - would this be too much of a pain, assuming it isn't obvious you are working flat out at rush hour and the airwaves are full. Will you accept any leeway on speed without us asking, say 5 - 10 kts, if it allows us to keep a cleaner configuration for a bit longer, ?