I've put around 10,000 through my open gun and it still isn't showing wear. I had DLC done by Richter Precision and they offer double coating( highly recommend).
I've been running a ff3 on my open 9mm major gun and have not had any problems. The window is a little smaller compared to the rts2 but the main thing is to find what works for you and practice, practice, practice...
I have always been a fan of Burris products. I'm moving into open and I've noticed that nobody runs a Burris fastfire on their open guns. Why is this? Do they not hold up? Is the window smaller than the rts2, delta point, ect.?