Hi @Joe Fischer,
To find out how long it takes to process a report and other usage metrics, review the report server execution log. For more information, see Report Server ExecutionLog and the ExecutionLog3 View.
Also, you may use SSRS snapshot. A report snapshot is a report that contains layout information and query results that were retrieved at a specific point in time. Unlike on-demand reports, which get up-to-date query results when you select the report, report snapshots are processed on a schedule and then saved to a report server.
You may also refer to this blog to see if it is helpful.
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