Apple continues to send out exploit notifications and Lockdown Mode continues to grow to include more attack surface. It seems to be actively maintained, as opposed to a lot of other things that Apple has tried.
I’m actually glad to hear that! I guess my underlying concern is that not knowing the full breadth of modern iOS’ attack surface might make me complacent when evaluating whether there are any risks that Lockdown doesn’t cover, and that being constantly notified on updates might somewhat alleviate that.