A standard or custom record in NetSuite has fields that has standard lists or custom lists which changes based on process. These could be approval process or status changes. All these changes are stored on the system information.
In case if we need to find the duration of each status for which they were present in a custom record, NetSuite saved search has formula which will find the duration.
Also the a custom portlet or custom screen can show the entire system info changes.
Note: All status changes or approval should be sequential.