After you stop working with the modeling tool, an idle time passes and the current project is saved to a special file called the AutoRecovery file.
If the application is terminated normally, the AutoRecovery file is removed. If the application crashes, the AutoRecovery file is kept. On startup, the modeling tool checks for an AutoRecovery file. If it exists, the modeling tool suggests loading the project from this file.

To save an AutoRecovery file of the open project(s) when a system is not in use

1. Open the Environment Options dialog.
2. In the General pane, select the Save/Load group, and then set the Save Project Recovery Data on Idle option to true. 
3. Enter the system idle time (in minutes) in the Idle Time to Activate Recovery Save box. This is the necessary idle time in order to activate the AutoRecovery save.