Goldfish

Your average listener has the attention span of a gnat and the mind of a goldfish.  Never think they are hanging on every word, do not believe they have remembered the last time you told them about a story.  True you should refresh stuff but don't worry about some repetition.  With trails and promotions repetition is actually very important. 

I have already discussed using different ways of imparting a message combining live studio reads with recorded produced promos with, if your broadcast guidelines allow, editorial which is produced for the promo/trail.

My old boss Steve Orchard once said to me that once you are so sick of hearing a promo go out you are actually ill in the waste paper basket - only then are your audience starting to absorb the message you want them to hear.  He had a point.  Carry on broadcasting!