i had bad ones fail i just replaced when needed and with time they all failed on me. i carry extra's now just in case , its a real pain to get them pushed into the shock , some easy some not so easy

 

I see you are having the same promblems I am having with Pro Comp. A bad batch of both upper and lower bushings is out there, I have replaced shocks and bushings four times and am waiting for more tomorrow. There is a "silent" recall, I just wonder how widespread this is. Make sure that you check bushings on the front too..
Best of luck....