Do you swap them out? Have you had any problems with the bottom edges coming apart from the inside plastic of the case?
My favorite is the white silicone case. I'm on my 3rd one due to the problem with the bottom edges. I've found at least the problem with my cases. It was the taking off and putting back on but especially the way I was doing it. When taking off the case, I would push directly on the corners away from the phone. I found that this flexing would cause the silicone to come undone from the underlying plastic. So with this most recent case, I originally put it on and left it on. But then I had to take it off and on due to switching out screen protectors. This time around I pushed the sides apart instead of the bottom corners and have had no problems.
So if you love the silicone cases like I do mine, try my recommendation above and hopefully our cases will continue to be like new.