The experience of the majority of adult pianists who have played narrow keyboards is that they adapt to the new size remarkably quickly – generally in a matter of an hour or even less. Children generally adapt almost immediately. As many adults now playing stretto keyboards still have to play the conventional keyboard from time to time, their experience is that once they have gone through the initial adjustment process, they can swap between the two sizes immediately. They often only need one practice session, or brief warm-up, on the alternative size.
The experience can be compared with driving two different cars (perhaps one manual and one automatic), or violinists who also play the viola. The adjustment from the conventional keyboard and the DS6.0® (15/16) is almost instantaneous.
Contrary to common belief, playing a keyboard with narrower keys does not make it harder to go back to the conventional keyboard when one has to. The reverse tends to be the case – playing a keyboard that better suits your hands gives the pianist an experience of greatly reduced tension. This new knowledge helps to develop better habits and minimise tension on the larger keyboard.
In 2015, Boston pianist Anna Arazi won third prize in the Dallas International Piano Competition playing on a DS6.0® keyboard, after just ONE day of practice on this reduced size. (https://www.youtube.com/watch?v=tj1RNLn8K6g).
See also the videos on this page: You can adapt quickly!
