This recent thread may provide some information.
Or not.
In essence, it appears the starting point is one week of silence: There is no longer a 24-hour wait, nor warning. This is based on my experience this week, for which the GMs apologised.
Please note, that Blizzard has not updated their online documentation (as was noted above) and while others may be trying to assist, it is best to only listen to those paid by Blizzard (blue posts).
And they are not providing any details on this.