text: Title: Representations from representation_models are generated twice when nr_topics="auto". 
  Body: ### Discussed in https://github.com/MaartenGr/BERTopic/discussions/2142
  
  <div type='discussions-op-text'>
  
  <sup>Originally posted by **siddharthtumre** September 10, 2024</sup>
  Hi @MaartenGr 
  
  While using nr_topics="auto", I can see that the representations from representation_models are calculated after reducing the number of topics. This increases the run time as a LLM is prompted twice i.e., before and after reducing topics.
  
  I believe generating representations after reducing the topics should be sufficient.</div>
  
  That's indeed what is happening currently. I believe it should be straightforward to implement that so this might be a good first issue for those wanting to help out.
  
  For now, what you could also do is run the model first without any representation models and then use .update_topics without your selected representation model (e.g, LLM) to create the representations. Then the LLM would run only once and you get the same results.