@KIWI5, I breathe differently depending on the kind of deadlifts I'm doing. For a reset at the bottom, I inhale just before I pull, I hiss out some air to maximize intra-abdominal pressure through the lift, I finish exhaling then inhale at the top, and I release my air as the bar hits the ground. If, OTOH, I'm doing touch and go reps, after I inhale at the top, I hold my breath or hiss out a little as I'm lowering the bar, then hiss out more as I pull again. The top is where I reset everything, including my breath for touch and go.
In neither case am I inhaling as I lower the weight - I inhale at the top and exhale at the bottom if I'm dropping the weight, so it's multiple breath cycles. If it's touch and go, it's inhale at the top on every rep after the first.
But that will change if it's a high-rep, heavy set, e.g., see the video here
Double bodyweight deadlift
and notice that the first 6 reps are what I said for touch and go, but you can hear my breathing change at the end of the 6th rep. I complete the 7th rep on a single breath, but the 8th and 9th reps find me doing what we call breathing behind the shield and taking more than one breath as I lower the weight.
Please also note a couple of things:
Many, and probably most people will do better inhaling at the top and getting tighter and tighter as they lower themselves to the bar and then pulling without another breath at the bottom, and what I just described is the way we teach it here. I have a history - a severe lower back injury - and it's more important to me to be sure I have everything aligned the way I know I need it to pull safely, and I can do that better by setting up at the bottom.
Related to my point immediately above, my back is stronger than my legs. I can pull a more "by the book" StrongFirst style of deadlift at a lower weight, and could even pull fairly heavy that way, but it's important to me to use the form I will use in competition, which relies on my back strength, in my training for pretty obvious reasons - I want to practice what I'll do in competition.
-S-