Hi Tim,
I think several posibilities comes to mind here:
1) If your organization uses a Syslog server for centralized logging solutions, we can re-route the logs there.
2) For every execution, once complete, the option to download the logs is available at the execution monitoring of that specific flow

3) You can access the results of the workflow via web services API, providing you ran that flow through web services. There you can extract a flow execution summary and return parameters if you set those
to return various bits of information on the execution.
Since the data is small and compressed, we do not employ retention mechanisms on the execution information at this stage.
Moreover, it is retained in the database and will be upgraded/retained every time WFA would be upgraded.
Hope I covered all the bases and that the response works out for you.
Yaron Haimsohn
WFA team