Just looked and no cracking like what your pic's show is on my '05 TJ's plastic wiring covers. Still flexible and no signs of brittleness. My TJ has 69k mi and has been in FL for about the last 3 years. Before that, it was iin IL since it was new. Maybe your more severe weather in OK contributes to your problem. Also, since I just got this TJ a couple of weeks ago, its possible that mine have been replaced by a prior owner.