Risk Based Inspection and Reliability Centred Maintenance are concepts that make extensive use of NDT results. The accuracy of the different parameters in such, often probabilistic methods in combination with fracture mechanics, determines the reliability of the results. The more accurate the inspection results, the more reliable will the remaining life time and the Safety Hazard calculations be. This paper will discuss several case histories in power generation, construction, offshore and (petro-)chemical industries where, because of the high accuracy of sizing, advanced techniques such as Time Of Flight Diffraction (TOFD) and C-scan mapping were used to establish the true condition of plant and to calculate its remaining safe life period. These results form the basis in cases for inspection interval and lifetime extensions. Examples will include inspections of Keyways in turbine rotors, corrosion and erosion in gas plants, root corrosion in flow lines as well as HIC and HHA in vessels and piping. In each case, the cost effectiveness can be demonstrated. As the useful lifetime of a plant begins when the plant is newly built, the role of baseline inspection of new plants will be discussed.