@Buzz you may well be right. Given that the majority of the time the aircraft is loaded in the sim, it will be in a running state, that approach won't make much of a meaningful difference vs a failure timer that only runs when engines are running.
Nick said there's a reason for real inspections being "based on calendar months", which I took to mean that all the elapsed time between flights would be considered for failure generation when you next load the Duke in the sim, but I may have read too much into it.
I suppose one way to test might be to set my computer clock to 1995 (furthest back Win10 will go), reinitialise the Duke by deleting any saved/state files, then load it in the present day and see if any failures had appeared. But I'll just wait and see if Nick clarifies first. If your idea is right, then maybe my idea can go on the wishlist instead - perhaps as a toggle option