I would tend to think that a 5% per year goal is more reasonable. Smaller incremental goals always appear to be more attainable, while more radical goals may actually be more difficult or impossible to acheive. Although there are lessons to be learned from every failure, not being able to reach an overly aggressive goal may harm the image of a company or department, or possible harm employee morale.

Additionally, short term goals are more trackable. A projected year end goal may be broken down into quarterly performance metrics which give managers a snapshot of their firm's progress. Though not impossible, it is more difficult to break down and track the progress of a goal over a longer span of time.

I think that a "slow and steady" pace will add more value to the company over a long enough time line. As processes become streamlined, the same company can perhaps be shooting for even better numbers per year than previously attainable.