The Egg exists to make Watanuki forget Yuuko so he can move on, but he refuses to use it. Even though he’s now powerful enough to leave the shop, he chooses to stay and wait for her, valuing his memories more than his freedom.
Lately, the Tsubasa (TRC) crew is shaking up the multiverse, which seems to be breaking the "old magic" Yuuko left behind. This is likely why Watanuki is finally sensing her again—the world’s rules are changing, and his long wait might finally be reaching a breaking point.
Since watanuki refuse to forget Yuuko, hence, all Doumeki's keep saying its not time.
I think, unless Watanuki himself choose to forget or if circumstances requires him to, that's the time the egg will be use.
Wait wait wait what's going on??? I don't get it. Why is doumeki's grandchild the one responsable? And when is that damn egg gonna do something?