From what I have seen with my ducks ( I have had a lot) the big one should get use to them over time. It might take some time. I only have one that had to be kept separated for good. That one was eventually gotten rid off.
I had always wondered. I know this is not a goose but I have a khaki duck that is 7 and still lays in the summer. Her production has gone down due to age.
I have read best production is up to 6 years. I have a 3 year old buff and she is still laying well. I would have to flip though my goose book again to be sure though.