100 frames, yes, that would be too many, the animation would simply run too slow, but after watching your small clip, I've noticed that it isn't a 100 frame walk cycle as he takes 3 steps during the 100 frame period, i.e. 100/3 = 33 fp second walk cycle.
As for feeback, it's looking good but a bit static and slow moving, try removing a couple of keyframe and making it shorter, like 24 frames per second, so the whole step will happen over that 24 frame period, this will help make it look a lot more fluid as well.