On the titanium, it definitely has a cycle life, which is directly effected by spring load. When the titanium gives up, the center will drop out. The keepers usually stay intact, inside the center. Usually the last step on the inside starts to crack, and eventually breaks away from the outside part. If it has not happened to you, you just have not run them to the point of failure. Tool steel will have a much longer cycle life than titanium.
Scott, I've been working on FE heads for most of my life. There are FE valvejobs, and there are infinite other ways to make a cutter. I called it a Chevy valvejob because it looks like widths and angles commonly used on Chevrolet and other aftermarket performance heads. That stuff seems to work on Chevrolet heads........I just know I have some designs that work better on FE heads. Some of my junk works on the other stuff, but I created the cutters I use testing only FE heads. I have several cutters that work for various ideas. I'd call mine FE cutters, and I call the others Chevy cutters.
I have flowed the GM LS7 CNC heads, and they have similar characteristics. The short turn is part of the "back up", but the hook contributes also. If you take the hook out, it will help the .600-up numbers, and it hurts the 3-4-500 numbers. I am sure the same will happen on this FE port, as they are very much alike.