For my part : I use the minimum keyframes as possible because each time you use a keyframe the camera speed change and thats need a lot of precision to make the transition smooth, especially when you put multiple keyframes close from each other. To make transition between two keyframes smooth, try to know keep the same distance-frames. For exemple, if you move your camera for 10 meters, wait 100 frames to put the next keyframe.
Well, I can understand that, but most of the time I don't wanna risk it on the transition part, so I still follow the 30 frame rule and keep close to each last keyframe and while editing just crop it to fit the transition. But if it works for you that way, than all's fine with the world. : )