Another caveat is that these classifications were often made by philosophers for whom virtue represented the highest good (so be careful when it is about Pleasure or Piety for Gods) .
I would say that's the most important point, and if forgotten it turns the whole classification process into a problem rather than a help. I like to outline and classify things too - so long as I don't forget they the purpose of the outline is to help in application, and not to uncover some hidden power from the classification itself. It's easy to get lost in classifying and the Stoics are a great example of not seeing the forest because they spend too much time classifying the trees.