I frequently see delays in all kinds of notifications and haven’t deliberately tried to test response times recently. I did see the offline notifications recently for the Cam OG that I was testing for offline spotlight function after I completed my test and took that down. I think it happened within minutes—didn’t think it was >30 but I wasn’t really expecting it when I saw it and don’t know how long it had actually been since I shut it down.
When I did shut it down, I navigated to its Live Stream screen and tapped Turn Off first before unplugging. I don’t know for a fact that this helps, but I figure it’s probably better for the microSD card so that the camera can finish any pending write operations before I cut power. I would think that would be an indication of an intentional user action—like the reboots mentioned previously—and I received the offline notification anyway, which is another reason I think they’re probably based on time.
I imagine, too, that this sort of thing could be useful for shared camera situations, like when some users have reported spouses or roommates turning things off. If the owner account has these kinds of notifications enabled, then the owner should get a message about a camera going offline even if a shared-access user “intentionally” turned the Cam off.