When is this a problem?
Each year that is included in the model calendar increases the size of the model. When used for planning purposes, it's likely that only certain data sets are needed, leaving many empty cells.
Why is this a problem?
It is unnecessary to increase the model calendar years when Time Ranges are available.
How to correct:
Use Time Ranges for data that are earlier or later than the current model calendar.
Anapedia: Time Ranges
Introduction to Time Ranges