Here is a recap of where we are in this discussion: Business plans formalize an understanding of the task with appropriate analysis leading to a plan_of_action. Not all business plans are for profit motives. Business plans are for an enterprise effort and not focused on disciplines/departments, e.g. Marketing plan, sales plan, HR plan, supply chain plan, etc. Business plans are a great vehicle to build a team effort. Plans can be utilized for formalizing metrics relative to achieving goals and performance measurements. Some complex plans might include a Project Management professional. There are internal and external audiences for business plans. Most external focused plans are for outside funding of projects. Be mindful of the 'tone' the plan projects to the reader. Tone refers to the impression a person gets from reading the plan; a subliminal feeling about the plan.
Then there are the moments when something seems to be going wrong, when one or more areas of the business just don't seem to be working. Cash flow is anemic or the marketing message is flat. Perhaps customers have shown a marked interest in only one particular product or service, ignoring all your other offerings. This means it's time to revisit your business plan, more precisely it's time to revisit the questioning process that helped you craft your plan.