Question
How can I retain compressed domlogs for longer than one month?
Answer
You can disable the "Remove the previous month’s archived logs from the user’s home directory at the end of each month unless configured by the user" setting within Home »Server Configuration »Tweak Settings inside WHM.
Disabling this option will require you to manually remove the compressed log files for your users. You can als manage this on a per-account basis within the Raw Access interface in cPanel.