Life cycle costing relies heavily upon a wide variety of information and data including the choice of appropriate discounting rates, the selection of relevant building life expectancies and the assessment of the lives of the different building components. The characteristics of such life expectancies are not so much a question of how long a building or a component may last but, of how long will they be retained. In theory, the life expectancies of buildings may be almost indefinite, if they are correctly designed and constructed and properly maintained throughout their lives.

However, in practice, their lives are frequently much shorter due to physical deterioration and obsolescence in many of its different forms. A major question to be resolved, for those involved in life cycle costing, is the life expectancy up to a major refurbishment phase. This is arguably of much greater and crucial importance than overall building life expectancy alone. The different kinds of building types and their respective uses each have different refurbishment lives. Evidence exists that clients are themselves poorly informed about the expectation and reality of such time intervals.