Hi Seika,
You can change the session parameters if you're playing on the Brain
Workshop version of DNB so that instead of 20+n trials per session,
you can have x+n trials per session (where x is any number of your
choosing -- example: x=500 for me today). If someone takes a 1 minute
break between sessions, doing all the training in one or 2 big blocks
should save about 20 minutes per day or alternatively allow for that
much more training in the same period of time. In addition (at least
for me), it seems to have conferred the ability to focus on the DNB
task for longer periods of time. I normally play with speed settings
at 1 to 2 seconds per trial instead of the default 3 seconds, so
that's another way I'm able to get in more trials within a limited
amount of time.