I understand very well what you are saying. I don't really look at my Aikido "changing", but rather, I like to think that it is evolving. My Aikido today is not what it was even 5 years ago. When I attend a seminar, I try to do what is being shown. I try to look for what is the same and what is different. I then try to learn from that experience and incorporate it into the foundation that I already have.
I remember being at a seminar where Chiba Sensei was teaching. He made a statement that really hit home with me. He stated that we should never get stuck in doing things one way, but that we should always look for a better way. So I am always looking to improve my technique, and sometimes that may come from a very unlikely source. But in order to do so, you have to keep an open mind.