Strategic objectives are the long-term, broad statements that create the framework for cascading short-term goals. With too many strategic objectives a strategic plan gets unruly.
A good, quick guide is to have one strategic objective for each of the 4 areas of The Balanced Scorecard: Financial, Customer, Process, and Employee Learning. An even shorter answer is to keep the number of strategic objectives to less than 6.
Trying to gain adherence to balanced scorecard.