Is manual cleanup of unused interest groups required in Photon Realtime, or can custom properties replace them?

Goal: Determine whether developers should manually clean up unused interest groups in Photon Realtime or rely on custom properties for event filtering.

Constraints: Interest group subscriptions are not persisted across reconnections, the server supports a maximum of 255 groups per client, and there is no built‑in mechanism to automatically remove unused groups.

Uncertainty: The documentation does not prescribe a lifecycle strategy, and community discussions are split between manual management and using custom properties for similar filtering.

Questions: Should interest group cleanup be performed explicitly after each room session, or is it acceptable to let groups linger until the 255 limit is reached? Does using custom properties eliminate the need for interest groups altogether?