A computer-implemented computer shut-down method, comprising: identifying that a computing device has been moved from an open configuration in which input and output mechanisms on the computing device are accessible to a user, to a closed configuration in which at least some of the input and output mechanisms are inaccessible to the user; identifying a first state of at least one variable at the time the device is moved to the closed configuration, wherein the at least one variable comprises one or more of a state of an application on the device, a time of day, an orientation of the device, a motion of the device, a location of the device, a calendar entry, or a level of remaining battery; starting a shut-down timer in response to identifying that the computing device has been moved from the open configuration to the closed configuration; waiting a predefined time period, as established by the shut-down timer, and determining from the shut-down timer that the computing device can be transitioned from an active state into a sleep state in which power consuming components of the computing device are powered down; and transitioning the computing device from the active state to the sleep state upon determining that the computing device can be transitioned; wherein the predefined time period is a delay determined by a delay model based on the first state of the at least one variable, wherein the delay model determines the delay by: determining second states of the at least one variable when the computing device is closed based on snapshots of the computing device taken at closing events; and correlating the second states of the at least one variable with durations determined by times between the closing events and next reopening events, wherein the delay model determines a first delay for the first state when correlated with a first range of durations and determines a second delay for the first state when correlated with a second range of durations, wherein the first delay is shorter than the second delay, and the durations in the first range are longer than the durations in the second range. identifying that a computing device has been moved from an open configuration in which input and output mechanisms on the computing device are accessible to a user, to a closed configuration in which at least some of the input and output mechanisms are inaccessible to the user; identifying a first state of at least one variable at the time the device is moved to the closed configuration, wherein the at least one variable comprises one or more of a state of an application on the device, a time of day, an orientation of the device, a motion of the device, a location of the device, a calendar entry, or a level of remaining battery; starting a shut-down timer in response to identifying that the computing device has been moved from the open configuration to the closed configuration; waiting a predefined time period, as established by the shut-down timer, and determining from the shut-down timer that the computing device can be transitioned from an active state into a sleep state in which power consuming components of the computing device are powered down; and transitioning the computing device from the active state to the sleep state upon determining that the computing device can be transitioned; wherein the predefined time period is a delay determined by a delay model based on the first state of the at least one variable, wherein the delay model determines the delay by: determining second states of the at least one variable when the computing device is closed based on snapshots of the computing device taken at closing events; and correlating the second states of the at least one variable with durations determined by times between the closing events and next reopening events, wherein the delay model determines a first delay for the first state when correlated with a first range of durations and determines a second delay for the first state when correlated with a second range of durations, wherein the first delay is shorter than the second delay, and the durations in the first range are longer than the durations in the second range. determining second states of the at least one variable when the computing device is closed based on snapshots of the computing device taken at closing events; and correlating the second states of the at least one variable with durations determined by times between the closing events and next reopening events, wherein the delay model determines a first delay for the first state when correlated with a first range of durations and determines a second delay for the first state when correlated with a second range of durations, wherein the first delay is shorter than the second delay, and the durations in the first range are longer than the durations in the second range.