A little late to the party on the forums, but I got my Rugby Pro a couple weeks after they were released about a year ago. I got it for the durability considering I work on a golf course.
Averaging twice a day (that's a very a low ball estimate), opening and closing the cover has not been an issue at all. I was worried about it myself, but if you look real close at the connector that holds the covers on it's a more flexible material. Not the harder plastic of the covers themselves.
I couldn't be happier with mine. No issues at all with durability. I actually drop it constantly and have destroyed two screen protectors to find when I took them off the screens glass didn't even scratch. (Once I was standing on it in a parking lot).
It is was well worth it working in the rain and heat all summer. On stormy days I laughed while I watched my coworkers dig out zip lock bags for their phones.
