I have a day job (nothing to do with music) so I:practice after breakfast 7am - 8am; andpractice after dinner 7pm - 11pm (with my breaks on the hour).
Uh, concentration is fine, but a lot of early piano training is building up muscles and coordination.
Once I had learned a piece enough I had it memorized with my lower brain, I would sometimes read a novel at the same time as playing, building up speed day by day.
My fingers are still pretty coordinated, although I'm having to work on strength training again.