@RGJ based on multiple requests from other users:
couldn’t this plugin of yours be used as the foundation for a new plugin that deletes topics in a particular category if they are older than N days, set by the user?
If your plugin is already scanning topics, wouldn’t it possible to set some rules that say:
If category is X, scan for topics where the creation date and the current date is more than N days, and if so, delete them.
I don’t know the ins and outs of creating and changing plugins, but this would be a great addition.