Not too many, to be honest.  A few because they took the client’s side on a bad report or kept needling for details that were contested on my end, several that lost clients that were good for me.  I only work with RBG because their shops are close to me (not recently, though) and trailer checking is all I do beyond that. 
I never went with the advice of signing up with everyone in sight.  I found enough early on and stopped there.