There is no canned one-size-fits-all answer to this issue. Standards define the requirement and act as a guide, but the path you take is based on your application – and the particular solution must be driven by the Performance Level (PL) generated via a risk assessment.
Click View Project button to see some helpful examples. This will help you understand the standards and help you identify a starting point to different ways you can take to arrive at your “safe” answer.