I don't know about you, but the Wacom fat-pen that comes with the Bamboo set cramps my hand like crazy, so I can't do more than 8-10 minutes worth of Skrittering in one stretch. So, I take a few 1-2 minute breathers while practicing to let my hand wake back up. When I return, I usually have to repeat the last two or three characters I finished from before the break. It doesn't seem to matter whether I got them right or wrong the first time, if that matters.
Am I the only one noticing this?