The total useful life is an important parameter in determining the value of real estate, which is not only directly included in the calculation procedures for determining the market value, but also affects the data relevant to the valuation derived by the valuation committee. Previous guidelines, including Annex 3 of the German guideline for determining the value of material assets (property), provide only superficial indications for a more precise determination without going into regional or market-specific factors, which is why the total useful life is only used as a model parameter. This often results in a divergence between the actual observed useful life and the theoretical assumptions made in expert reports. In this paper, influencing factors on the total useful life are first identified through the analysis of previous studies, an evaluation of statistics and the conduct of expert interviews in order to specify the term "total useful life". The application here takes place with the focus on office buildings and determines not only important parameters but also their characteristics. The evaluation matrix for the total useful life derived from this makes it possible for expert committees and appraisers alike to consider the total useful life in a differentiated way and thus provides an instrument that enables the total useful life to be brought into the evaluation beyond the specifications of the current guideline no longer as a mere model size, but as an actual influencing factor.