The Balanced Scorecard is a dynamic tool. A tool as flexible as your management requires and designed to be simple enough to be tweaked as the dynamics in your business and the business environment change. To create a set of strategic and operational objectives that remain static over time is a recipe for consistent, non-competitive performance. Things change. Things change all the time. Your perspectives and objectives will change and need to be monitored for validity on an ongoing basis.
Traditional annual timeframes of review should not be considered valid. Unfortunately our reporting paradigms are based on accounting and government taxation requirements, those requirements have no correlation to business performance. If a perspective, objective or metric needs to be changed, then change it now, and don't place it on hold until the next reporting cycle.
I am constantly amazed at how many business owners or managers seem to feel that the holy grail of change starts at the beginning of a new business year. Such reporting mind sets are destructive to successful rollout of initiatives.
As a matter of process, it should be understood that a difference exists between Strategic and Operational measures. As a general rule Strategic direction does not alter. Rewind back into business history and you'll find businesses will fundamentally have the same strategic intent as had occurred at inception.
Operational metrics do however change. If your Strategy is constantly changing then you need to revisit your strategic formulation process for a better understanding of both the process and your business.