Bamboo deployment log retention: no per-project override separate from global expiry?

Goal

We run Bamboo (Server/Data Center) and need to diagnose failed deployments from their task logs, sometimes weeks after the failure. The problem: global expiry settings appear to delete build and deployment log files after a defined period, leaving the result record but no task-level output to inspect.

Constraints and uncertainty

From what I can tell, log retention is governed by the global expiry configuration, and there is no built-in way to keep logs longer for one specific deployment project while letting everything else expire on the normal schedule. Extending global retention works but increases disk usage across all plans. Exporting logs externally before expiry is possible but adds operational overhead.

I have not found a documented per-deployment-project retention override in recent versions, but the exact expiry options and labels vary between Server and Data Center releases, so I may be missing something.

Questions

1. Is there any supported way in current Bamboo versions to set log retention per deployment project, independent of global expiry?
2. If not, what is the recommended approach for preserving failed-deployment logs long enough for later diagnosis without inflating global retention?
3. Does expiry remove only the log files, or also the deployment result metadata needed to identify which task failed?