Hello Wildman, Far from been a goose expert, we both incubate eggs and let nature take it's course, in our experiance the goose waits till it has enough eggs then starts to sit and like you have already said they seem to increase the time they sit the more time goes on.Also when the goslings have hatched we now take them away from their mother. I know this sounds cruel, but last year one goose hatched 8 goslings. Day one flattened 2, day two flattened 3, finished the rest on day 4. They are very protective mothers but a little bit clumsy.Hope this is of some use