@veloman I think it's about 1 week that it starts to not taste that sweet. That's when the bacteria have consumed a lot of the lactose. You can obviously drink it still as it only ferments in the fridge and you like it still. It doesn't really go bad, it only ferments.
@Swansven i get duck eggs from my nearest farm, but i much prefer the taste of chicken eggs, for some reason they don’t sell chicken eggs at all, but the duck eggs are high quality and huge yolks so I might stick to them until I find another farm