While I personally don't use projections disks as part of my DMB habit, the earlier posts in this thread reminded me of something Bill James wrote many years ago:  that in trying to predict the outcome of a World Series, the players' performance over the past 3 seasons was a more reliable basis for prediction than their performance in the same season as the World Series.  So I guess that would bolster the argument that using projection disks is no less realistic than using season disks, in the sense of producing a reasonable outcome for the season.