I don't know if this is any help, but it sounds from your post that you are very into dream-control. Now, this is no bad thing of course, but from my experience, a much better way to prolong and stabilise lucidity once you gain it is to actually be very passive. Rather than trying to make things happen in the dream, just stop, control your excitement, maybe look at your hands or rub them together to calm yourself, then look round at the dream-world. Try to focus in on small details, and touch things, feel all the different textures, see if you can hear any sounds, etc. Once you have done all this, you should be much calmer, and then you can start trying to make things happen in the dream.

Also, when you say you think perhaps your constant RCs may be dulling your sense of dreaming lucidity... maybe you should experiment with different RCs. What I try to do (and this perhaps isn't strictly an RC but I think of it as such) is to emulate a sense of 'waking lucidity' whenever it occurs to me to RC. It's hard to explain, but I deliberately bring on that peculiar feeling you get when you become lucid in a dream. I try to make myself feel that way, and then I look at the environment around me in a super-critical way, not just trying to see whether I'm dreaming or not but actually pretending that I'm dreaming. Then I try to make things happen, e.g. if I'm walking down the street and see someone, I try to make them vanish with sheer thought. Or I try to make things appear, or I will myself to fly (I do this all in my mind, no physical action, because if I was dreaming, no physical action would be required to do these things). When none of these things happen, I know I'm not dreaming, and I let go of the peculiar lucid feeling and go back to real life.

I hope that makes sense. Basically, I do a RC where I assume that I am dreaming, and then try to prove that I'm not, rather than assuming that I'm awake and trying to prove that I'm dreaming. Hope some of that helps.