For any existing features like a setting, API, CRD, when deciding to deprecate or even remove it, should follow the below policy.

• Deprecate a feature in a patch or feature release. The feature should still work until it is removed later.
• After deprecation, remove the feature in the just following feature release with the upgrade migration to ensure a smooth upgrade.
• When deprecating or removing a feature, need to update the important note (https://longhorn.io/docs/latest/deploy/important-notes/) and also upgrade doc if needed in the doc to describe the change and encourage users to use the new setting instead.

Can refer to an example https://github.com/longhorn/longhorn/issues/5620 about deprecating allow-node-drain-with-last-healthy-replica in 1.3.2/1.4.2 and removing it from 1.5.0.