When planning a new application for deployment, it is important to include a business continuity plan (BCP) and assign the tier level even at the early stages of the project. The reason behind it is more than just to determine how much to budget for a fully functional BCP, but also to ensure that the application is reliable.
Often, important applications that have high visibility must have a robust production environment to prepare for any catastrophe. Critical applications should have BCPs should something bad happens to that environment.
Assigning the tier level for the application goes hand-in-hand with BCP. The deciding factor for most BCPs, especially if there are limitations on budgets and resources, is the tier level. High risk tiers such as tier level 1 and 2 applications must have a good BCP.
Having BCPs for these types of applications would guarantee that the applications will be back up and usable at a given amount of time mentioned in the plan.