Data improperly prepared will impair your analytic processes. Data collection issues abound. Data is unreliable, inaccessible, dirty, sparse, biased, too small, too big, and altogether incomprehensible. Planning is the key to developing a robust analysis.
The real focus of your analytics data design should be reproducibility and speed. What use is your data if it takes days to get a simple answer from your best analyst, or your two best analysts generate two different answers?
Speed and reproducibility constraints on your growth. Can an organization grow and still keep the information it needs at its fingertips? Though time consuming, sufficient planning mitigates the accumulation of data and complexity.