Your resident musicologist here with a note about "recycling". EVERY and I mean EVERY composer recycles compositions or themes at one time or another with maybe the exemption of Mozart. Just about the entire Handel "Messiah" came from various organ concertos, operas, church music or other smaller compositions. Because why not? You got a good tune, why not re-use it? When you have to churn out a big output in short time frame why not rework what you've already done?
From what I understand, Cobert made the decision to "recycle" his themes, not Dan Curtis. He was working on Dark Shadows and Dr. Jekyll and Mr. Hyde at the same time. Cobert is a really good film/TV composer. Thus, why wouldn't different movies want to use his great themes? And, why shouldn't he be able to use the themes he wrote for different projects?
It always makes me happy to recognize them in different productions.