When you say aged 12days is that the meat already cut from the breast?
Sometimes, sometimes not. Here is what I do:
Step 1) After hunt, ducks go on ice in truck and they stay on ice till I get home, which could be days.
Step 2) When I get home, ducks go right to garage "man" fridge, breast up. Or from ice chest strait to step 3.
Step 3) Pluck breast unless really shot up, then just pull skin off. Get all blood clots out, even if you have to tear apart breast or cut into cubes. Make sure no feathers, and rinses meat with water really good.
Step 4) Soak in water 24 hours, I do not mess with brine. (top right in pic above)
Step 5) Drain water, maybe rinse again, then get rid of all excess water, paper towel helps.. Pepper up in tuppawarewith, top on tight or loosely on to breath and age (pic above top left).. Every day, give the meat a flip or stir, it creates its own marinade, pour off excess though.
The whole process is 1 to 2 weeks, my preference is to get to step 4/5 as soon as possible, but I do not think it matters. And you can freeze anytime, I mark "Date shot" and "Date Froze" so I know how long they where aged before they were frozen.