It seems to me that the only reason that in most cases people don't use lucid dreams to live through years worth of events (where as it is actually rather common during non lucid dreams) is because upon attaining lucidity one comes to the "usual" state of mind, not used to using conceptual thought.

In fact, I think lucid dreams are a valuable tool for training conceptual thought by will instead of the oh-so-inefficient verbal and image-based thoughts most are used to.