Hi Jazz. My mom dresses hers at 6 monthes, which is the perfect dressing age, and says they are not yummy after 2 years.
There is a time at 4-6 monthes when they are very hard to pluck, as the feathers are changing. You have to do it by 4 mths (but they are too little really, a bit boney still), but 6 makes a plump tendor young goose that is easier to pluck.
Now, are you saving the down, or tossing it all? Waxing is the best way, like with ducks, to remove the down if your not saving it. If you are, get some freinds and booze, and dip them into hot water, and pluck feathers, then hand pluck down. Put it into cotten bags, so you can wash it, but it won't become lost. If you want, you can dress and skin the bird in one piece, and the feathers are quite lovely then for coats, or baby coats....
I was raised eating ducks and geese (and every other crawling, creeping, or running domestic critter).
C u around, girl.