I probably simply do not know the correct search terms for that issue.
At the moment, on my on-premise installation, I can see completed processes for around 48h, but we would love to move that up to 168h. Can I do that via the Admin Console? Or do I have to adjust some config file? In any case: Where do I do that?
Discussion posts and replies are publicly visible
All of the other responses address your actual question, whereas I want to challenge the underlying thinking here. Why do you want to increase the amount of time a successfully complete process instance remains in memory? Given that an application server has a limited amount of memory the objective should be to try and remove completed instances from memory as soon as possible. Processes that are still in flight or have problems are not candidates to be removed and it is right and proper these remain until they are successfully completed.
If your objective is to provide some means of introspection as to what has happened then a database-based audit trail will be a better option long-term as the data can be kept for a much longer period without affecting the performance or scalability of your application.
What is your use case for wanting to extend the period of time completed instances reside in memory?