I had a little trouble working out the hair for the characters of the Pandora CGfilm. At first I went all out. I mean I had dynamic, bouncier than necessary hair for my characters, that looked silky shiny with lights were added. Well, to render one frame of one of these characters took a little over five minutes. I have over 700 frames for one scene. Painfully slow but what great hair they had.
I re-evaluated the use of hair to the overall story and I found I will use a some dynamic hair, but fill in with "hair planes". I'm still working out the kinks on this but I now have hair rendering down to a little over two minutes per character...per frame (sigh).