I can see when the sensor is getting ready to fail by looking at the CGM graph. When the sensor is still working normally, the graph is a smooth line, rising and falling with the blood glucose. When the sensor is starting to fail, I see jitter in the graph: the dots jump up and down around the line rather than progressing smoothly. That’s the sign for me that it’s time to change the sensor. For me that’s usually after 12 to 15 days of use. Other people get different wear times. I usually restart the sensor on day 6 and day 12: just stop sensor, start sensor; easy as can be. But I use a variation of “the microwave technique” so I basically never need to go 2 hours without CGM data, either when restarting a used sensor after 6 days, or when starting a new sensor after the previous one is starting to fail. G5 data with no 2-hour warmup for new sensor (using Dex app on phone and Dex receiver)