Try three or four days.
Then the skins need to be 'tuned' to the inflation rate you're after.
Then properly treated and stored.

Jon Carney's 'Book of Secrets' is an excellent source.

I use chicken eggs and have no problems with them.

In the 1970's I toured with a Clairvoyant Hen which I claimed laid eggs containing predictions - In my book Magictales (Leaping Lizards 2006) I provide an original Egg on Fan presentation with comprehensive instructions for making egg skins from duck eggs.

Leslie