Well First and foremost I feel that a guy who gets gassed quickly in sparring because of poor breathing is in trouble during a fight.

You must get your fitness up so as to have sufficient fitness to get by without worrying about breathing at all.
I've had my nose broken in the ring and twice had it full of blood making breathing impossible, so I had to work with impeded breathing.

As for when to exhale, again I feel thinking about it is a problem, just box as well as you can man and let the breathing come with it. I only concentrate on my breathing between rounds.