A method of determining thermal stability of an upper surface of a substrate support assembly in a plasma processing apparatus includes: before processing of at least one substrate in the plasma processing apparatus and while powering an array of thermal control elements of the substrate support assembly to achieve a desired spatial and temporal temperature of the upper surface of the substrate support assembly, recording pre-process temperature data of the substrate support assembly; after the processing of the at least one substrate in the plasma processing apparatus and while powering the array of thermal control elements to achieve the desired spatial and temporal temperature of the upper surface of the substrate support assembly, recording post-process temperature data; comparing the post-process temperature data to the pre-process temperature data; and determining whether the post-process temperature data is within a predetermined tolerance range of the pre-process temperature data.