What I was looking for
How runway alerts should behave when someone switches them on late.
What I found
CreditWatch warns at 12, 6 and 1 hours of runway. If runway is already 4 hours and you enable the 6-hour alert, a naive build fires immediately. An alert that reports history looks the same as one that warns.
The shipped behaviour refuses to arm any threshold below the current runway, and says so in the dialog.
The move
For anything that warns, I ask what happens when it is switched on after the event, not before.