Mine always seem to get hairline little cracks running out of the grip, but these never get any worse. Had a Hell 4 Leather for 4 years (using it twice a week every week) which did this within about 6 months, and never got any worse. Given, it does have a small handle and relatively thin shoulders... Also had it happen on every Warsop I've ever owned, and they have massive oval handles and no concaving high up on the bat, so not sure what it could be.
Might be less pronounced if I middle it once in a while rather than one on the stickers, one on the toe, one on the stickers, one on the toe......