I was driving down a mountain the other day (roads and moderate off road) when my brakes felt like they were going out. It felt like the pedal was bottoming out and the car was still rolling, though slowly. When I got out to look at the things, they were smoking a little and felt really hot. I was riding them more than I should have in 3rd so I dropped it down to 1st after they cooled and had no probs. Is this something to be concerned about or is it common when these brakes get hot?

 

That sir is called brake fade, when brakes get hot they loose their grip, they get hot enough they wont work at all.
That is why you use engine braking when going down a really long grade like that.

To keep brake fade from happening use short sharp jabs on the brake pedal, do not ride it.
You want to stay at 50mph for example, but are creeping up on 55, press the brake pedal firmly and slow down to 45, release brake pedal and coast back up to 55, hard on brake pedal again, repeat.
By "jabbing" the brakes like that they are going to get hot, but as soon as you release the brake pedal they will cool back off.
And of course make sure that you are going slow enough for the road conditions.
You can be going 10mph and still overheat your brakes.

Make sure that you are in a lower gear on the trans to start with and dont be afraid to downshift the transmission, you wont hurt anything.
The transmission will not let you over rev the engine.