I use them (.223, .308 and .30-06).
I can't say they make the brass last longer as I don't really track number of loadings.
I shoot the .223's more than the other two. At some point the shoulders crack (usually shoulder, sometimes the neck). So far, not a single separation back near the base, as if the case was stretching.
My wife got the dies for me for Christmas one year. I didn't start using them till I had an issue with a new AR15 build. Had failure to chamber issues. I had been using Lee dies for a few years with no issues, built a new carbine and had almost a 5 out of 10 failure to chamber rate. Dug out my old Pacific .223 dies and got a slight improvement of 7 or 8 of 10 that would chamber. Grabbed the RCBS X dies off the shelf and got a 10 out of 10 to chamber rate. Put the Lee and Pacific dies away, pulled out the .308 and .30-06 X dies and have been using them ever since.