When you need to descend, you can: Use speedbrakes, fly faster, extend the gear early and/or extend the flaps early. You can also ask for vectors back around the box or a 360 to lose altitude.

If you are assigned 210 knots, you are supposed to stay at that speed until the assignment has changed. Often they will say "170 until 4 DME". Sometimes they just assign the speed, and we have to ask the controller (usually the next controller) if they still want us at that speed...the controllers forget about us....and usually they will let us slow down when we ask.

You may be sent down early at a "non-busy" airport if their airspace conflicts with some other airport's. For example, anywhere near Chicago you often have to descend early because of ORD/MDW traffic, even if you aren't landing there.