Yes, the RMAN logs are stored on the client under the "JobResults" structure. As such you can extend the retention of the job results location from the client properties.
From advanced settings go to the "Job Configuration" tab. In the middle of the window you will see a "Prune job results after" setting that is set for the default "7" days. Just extend that out to match your requirements.
From the documentation: Pruning Job Results
Ernst F. Graeler
Senior Engineer III