Short of archiving the emailed Executive Reports, I don't believe there is a way to consult past reports. The Astaro Report Manager (ARM) is an extra-cost package that might do what you want:
https://www.astaro.com/our_products/...report_manager
If you're interested in securing the Astaro logs, look at the 'Remote Syslog Server' and 'Remote Log File Archives' tabs of 'Logging >> Settings'. If you have a lot of existing logs you want to copy, then search these forums for WinSCP.
Cheers - Bob