We report on the reliability of micro-heating elements made on a polyimide plastic foil. Tests on the maximum power the devices could withstand before failure and their aging when operating continuously at a constant temperature between 200 and 400°C were performed. They demonstrated that the hotplates can operate at continuous elevated temperatures at very low-power for more than a year. The deformation of the hotplate during operation and the failure mechanisms were studied. Such investigation is of interest for the design of robust metal-oxide gas sensors on foil to be directly integrated into smart sensing labels.