Cactus / placentiformis

Some of my collections have not been in flower yet.
The photo is one of them, Discocactus placentiformis v latespinus f major HU640.
I bought seeds and sowed on 06/08/2007 and grafted several seedlings.
I degrafted one of them 2 years ago which is shown on the photo, 13 cm diameter.
I am not sure when I can see the flower.