What describes the length of time an improvement is expected to remain functional and useful?

The term that describes the length of time an improvement is expected to remain functional and useful is "economic life." Economic life refers specifically to the period during which a property or improvement can generate income or provide value before it becomes obsolete or no longer economically viable. This concept is crucial in real estate as it helps investors and property owners assess the potential return on investment and make informed decisions regarding property management and development.

Understanding economic life allows stakeholders to consider various factors that influence a property's longevity, such as maintenance, market conditions, and technological advancements. It is important in the context of appraisal and investment analysis, as it helps determine depreciation and the overall valuation of a property over time.