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.
Add a Snapshot to Report History
You may also refer to this blog to see if it is helpful.
Regards,
Zoe Hui
If the answer is helpful, please click "Accept Answer" and upvote it.