Brad's so good at ATOs that it makes sense to save the timeouts, to the extent possible, for the last 6 minutes or so, provided you expect the game to be close at the end.
I agree that at times it feels that he waits too long.
As for holding leads, it's a vexing issue but I think part of the problem is that whenever the team builds a big lead and then the other team makes a run to make it close again, that's going to stick out in your mind.
Sometimes, though, it's just part of the ebb and flow of the game.
Do the Celts actually fail to hold onto double digit leads more than other good teams? Do they tend to fight back from being down double digits more than other good teams?
The Celts are a +6.6 team overall. To some extent it speaks well of them that they tend to build double digit leads, in the first place.