I burnish all my bows, back and belly. It may help prevent splinters, but I do it more because it creates a compressed, very smooth surface that is glass smooth and repels moisture. (Splash some water on a burnished bow and you'll see how it beads rather than soaking in.) That's an added level of natural protection beneath the finish. Also, dyes and finishes won't cause the grain to raise if the bow has been burnished first.