mstram,
At 20nm on the glidepath would be at 6,000ft. Therefore if you have been descended to 3,000ft you could still be at 320 kts, especially in a smaller jet (737, A320). A larger aircraft (e.g. A330) has more momentum so you need to get configured earlier. My experience with the 737 and A320 is that gear down flap 15 (737) or gear down flap 2 (A320) is a pretty effective airbrake, but not on the A330 (gear down flap 2).