A lot of people ask, when should strategic planning be done and how often should it be done.
In a great article from   Free Management Library, this topic is covered well. 
 
The scheduling for the strategic planning process depends on the nature and needs of the organization and the its immediate external environment. For example, planning should be carried out frequently in an organization whose products and services are in an industry that is changing rapidly . In this situation, planning might be carried out once or even twice a year and done in a very comprehensive and detailed fashion (that is, with attention to mission, vision, values, environmental scan, issues, goals, strategies, objectives, responsibilities, time lines, budgets, etc). On the other hand, if the organization has been around for many years and is in a fairly stable marketplace, then planning might be carried out once a year and only certain parts of the planning process, for example, action planning (objectives, responsibilities, time lines, budgets, etc) are updated each year.

Consider the following guidelines:

1. Strategic planning should be done when an organization is just getting started. (The strategic plan is usually part of an overall business plan, along with a marketing plan, financial plan and operational/management plan.)

2. Strategic planning should also be done in preparation for a new major venture, for example, developing a new department, division, major new product or line of products, etc.

3. Strategic planning should also be conducted at least once a year in order to be ready for the coming fiscal year (the financial management of an organization is usually based on a year-to-year, or fiscal year, basis). In this case, strategic planning should be conducted in time to identify the organizational goals to be achieved at least over the coming fiscal year, resources needed to achieve those goals, and funded needed to obtain the resources. These funds are included in budget planning for the coming fiscal year. However, not all phases of strategic planning need be fully completed each year. The full strategic planning process should be conducted at least once every three years. As noted above, these activities should be conducted every year if the organization is experiencing tremendous change.

4. Each year, action plans should be updated.

5. Note that, during implementation of the plan, the progress of the implementation should be reviewed at least on a quarterly basis by the board. Again, the frequency of review depends on the extent of the rate of change in and around the organization.