Before you install your thermeristor, you should double check that you both purchased and received the working before installing. Apply the multimeter probes to both legs, and the multimeter should display the resistance. Below is some common themeristor temperature table. If it reading room temperature, if not or resistance is jumping you may have faulty thermeristor. If so, please contact us for RMA.
See more detail table: https://support.dremc.com.au/helpdesk/attachments/51120157954
Below table are Kohms Units
Average life of the be slinger thermistor wiring ~500-850 hours, we recommended replacing the wiring of the thermistor every 750 hours as preventative measure
The life the toolhead thermistor, depend if wiring is strain relief but usually last bit longer at 850-1250 hours but usually recommend replacing the wiring every 1000 hours for the thermistor in Ender 3/MK3 printer for instance. If the printer is using a toolhead printer, and the module is minimal wire strain, it should last the life of expected life of the each specific module but in our testing and experience most common failure point is wiring not the actual thermistor.