This paper presents the results of a study based on practical experiences and cases with regard to the need for maintenance of installed CP systems over the past 35 years in the Netherlands. CP is a proven technique for long-term protection of steel in concrete against corrosion. Corrosion can lead to significant damage to reinforced concrete and ultimately result in a reduction in the load-bearing capacity of the structure. Correct application of CP can prevent this. Over 35 years, CP has been successfully applied in the Netherlands to all kinds of concrete structures in the industry, residential buildings, infrastructure and even monuments. CP normally distinguishes itself from other repair techniques by its long service life and durability. With careful application and professional monitoring, a service life of 15-30 years or even longer can be achieved. Nevertheless, there have been applications in which the CP system had to be maintained in the shorter or longer term or even completely replaced. Although every application requires maintenance, this maintenance sometimes came completely unexpectedly or much too soon. This paper gives an overview of a number of such projects and identifies the causes and consequences (in scope, costs and effects) of the relevant maintenance measures.