I flew IAD-CMH on an ERJ recently (UX - Chautauqua) and about 20 mins before landing in CMH the landing gear was lowered. The pilot came on and said that we would be "heavy" and we needed to burn some more fuel, so they lowered the gear.

My question is, why would this happen? As far as I know, IAD and CMH did not get closer to each other during the flight. In the flight planning they would have planned for the distance, yeah? Even if they got all the shortcuts in the world, would that really get us there with so much extra fuel that we'd have to burn some before landing?

Any pilots know? The only thing I can think of is that the weather was really crappy and they loaded extra fuel in case we had to go to an alternate. But if that were the case, why did they start burning the extra fuel 20 mins out during the first landing attempt?