Conventional power plants will have to respond to the volatile requirements due to the fluctuating feed-in of renewable energies with an efficient and flexible operation. The resulting stresses are to be detected and assessed early on in order to ensure an optimal unit utilization and maintenance strategy from an economic and technical point of view. The two expert systems SR1 and SR::SPM continuously monitor the stress of 32 highly-stressed thick-walled boiler components as well as the superheated steam and hot reheat pipes. They achieve the following benefits at the site: reduction of the inspection effort for highly-stressed components; early detection of critical conditions; proof of the specified normal operation to authorities, TÜV (inspection agency), and insurance companies; important information on the component condition to enable assessment and optimization of the influence of flexible modes of operation.