An aerosol generating device comprising: a vaporiser configured to vaporise an aerosol-forming substrate ; a battery connected to the vaporiser; a control circuit for controlling the supply of power from the battery to the vaporiser; a memory for storing a usage record of the device; and a replacement indicator for signalling to a user that the battery requires replacement, wherein the control circuit is configured to: measure a voltage across the battery, compare the measured voltage across the battery to a threshold voltage and to generate an error signal if the measured voltage is less than the threshold voltage during an operation cycle, generate a no-error signal to update the usage record if the measured voltage remains above the threshold voltage during an entire operation cycle of the device; the aerosol generating device being characterised in that the control circuit is further configured to: store the error signals and no-error signals generated during a plurality of the most recent operation cycles of the device in the stored usage record, such that the stored usage record comprises a combination of the error signals and the no-error signals, and access the usage record and activate the replacement indicator if a total number of error signals stored in the usage record during the plurality of the most recent operation cycles of the device exceeds a threshold error value, wherein the threshold error value is at least one. a vaporiser configured to vaporise an aerosol-forming substrate ; a battery connected to the vaporiser; a control circuit for controlling the supply of power from the battery to the vaporiser; a memory for storing a usage record of the device; and a replacement indicator for signalling to a user that the battery requires replacement, wherein the control circuit is configured to: measure a voltage across the battery, compare the measured voltage across the battery to a threshold voltage and to generate an error signal if the measured voltage is less than the threshold voltage during an operation cycle, generate a no-error signal to update the usage record if the measured voltage remains above the threshold voltage during an entire operation cycle of the device; the aerosol generating device being characterised in that the control circuit is further configured to: store the error signals and no-error signals generated during a plurality of the most recent operation cycles of the device in the stored usage record, such that the stored usage record comprises a combination of the error signals and the no-error signals, and access the usage record and activate the replacement indicator if a total number of error signals stored in the usage record during the plurality of the most recent operation cycles of the device exceeds a threshold error value, wherein the threshold error value is at least one. measure a voltage across the battery, compare the measured voltage across the battery to a threshold voltage and to generate an error signal if the measured voltage is less than the threshold voltage during an operation cycle, generate a no-error signal to update the usage record if the measured voltage remains above the threshold voltage during an entire operation cycle of the device; the aerosol generating device being characterised in that the control circuit is further configured to: store the error signals and no-error signals generated during a plurality of the most recent operation cycles of the device in the stored usage record, such that the stored usage record comprises a combination of the error signals and the no-error signals, and access the usage record and activate the replacement indicator if a total number of error signals stored in the usage record during the plurality of the most recent operation cycles of the device exceeds a threshold error value, wherein the threshold error value is at least one. <EOS>