For that short of a steep descent I'd just ride it and my tandem team has 100lbs on you. TG's advice is pretty good but it takes developing a "feel" for what your bike is doing. I don't know if everyone has those skills or the inclination to learn them? Another alternative is to just ride down very slowly so that the brakes don’t have the opportunity to get really hot. Ultimately you have to go by how you feel. If you are concerned about it then you did the right thing by getting off and walking.