The lifetime of the project is the length of time that the subject matter of the project is functional and retain the required properties.
The life of the project is an important parameter for calculating the return on investment, sustainability and total cost of the subject matter of the project. The project is in most cases an investment project, ie. the development, construction or purchase and putting into operation of some technology, infrastructure and the like.
The lifetime of the project therefore indicates the expected time (usually in years) when the subject of the investment will be functional and will serve its purpose. At the end of the life of the project, either repair, renovation or cancellation of the investment must be undertaken.