Stupid question, here, Kev...
Why the "built-in" holds? Why not just have a continual countdown with 30-min. (or, whatever) built in to the total?
I'm an idiot but it seems to me like "Spinal Tap"'s "11."
In case something happens..
Holds are built in at specific times before you commit to doing more major things in the countdown. There are a number of steps that need to be overcome in any countdown, a hold is usually put in before a major step that could be irrevokable.