I went in with a 5243 build. Some things to note: charm got doubled up, since it had the most hanging points (leftover flashes) at the time of maturity. I wanted a 7 power / 4 charm split but I didn't get it.
I used about 1300 cards and only found around 30ish secret cards. I got ZERO flashes on the egg for finding extra life (yellow) tokens after the first few tries. I also used a lot of Don Giovanni cards, so I ended up at Stage 10+ a lot. This is probably one reason why I used fewer cards. In any case, I kept going until the egg stopped flashing. I started card ID when everything was at 0. I also stopped fortunes when the egg stopped flashing. Finally, the egg affinity changes to all four symbols during card ID. There seems to be no way to really control where it goes. I had hundreds of neutral character cards, and the symbol affinity still ended up random during ID.