1. A method of operating an infusion device operable to deliver fluid to a user based on measurements indicative of a physiological condition of the user provided by a sensing arrangement, the fluid influencing the physiological condition of the user, the method comprising: determining one or more signal characteristics associated with a subset of the measurements, the subset of measurements corresponding to a monitoring period; determining a reliability metric for the monitoring period based on the one or more signal characteristics; and providing indication of a maintenance condition when the reliability metric violates a first threshold.