I suspect that from a fatigue standpoint, which the mothership has more than suggested is the likely issue, that aerobatics is far less significant than, say, whether you operate from dirt, or grass, (or the Reno-Stead KRTS taxiways...just kidding) with a tail dragger. The other potential fatigue drivers would be prop vibration, as originally noted by Greg Hughes, and regular, frequent, moderate turbulence at high speeds.
My speculation, hunch, instinct, is that the preponderance of cracks are going to appear on tail draggers. Years ago, I owned a PIK-20D sailplane that had an AD to inspect and repair the lower rudder hinge bracket. Guess what the cause was? Trailering the glider. There is a significant amount of lead counterweight on the leading edge of the rudder, and road vibrations felt in the trailer produced a vertical cyclic load on the lower hinge from the rudder. (the upper hinge had a floating hinge pintle so it didn't share the load).
We are talking multiple thousands of load cycles applied to the hinge bracket. Not likely that even a thousand loops would do it. How many loops have you done?
