There are people like that. They will keep riding you for as long as you keep responding in a polite and reasonable manner. The tactic is to add progressively

There are people like that. They will keep riding you for as long as you keep responding in a polite and reasonable manner. The tactic is to add progressively larger delays to each response, while make them shorter at the same time. Start with a delay of a couple of days and progress to weeks. This works and it's very effective in discouraging this sort of behavior. The same works with for new tickets, but you can just close them after a week. Optionally add something like "Dully noted, thanks".