Improvement vs accomplishment

It's a tough one trying to come up with metrics for non routine tasks. You can't measure improvement of something that is a one off, or at least something that I haven't done before.
I'm thinking here of the mission completion. These are non routine tasks that draw me closer to the epic win. Playing the game (or at least being involved in developing it; I don't know which until more people start doing the same) definitely helped me with getting more done.

The metric for the mission completion is the path to Epic Win itself; there are questions that can help focus on getting the missions don:

• How can I achieve the Epic win in the least amount of steps (part of planning process)
• How quickly can I complete this in the limited time I have?

There are others, perhaps more effective than these that could be adopted.