I have not noticed this yet.
Here's a question for you though: When you have them installed, do you take any layers off? I like about 2 layers off mine, and then shaped to a dime radius.
Yes, I have about 1/2 the tip whacked off right off the bat. BUT, and I say this just semi-kiddingly, I have them installed upside down. And the reason for this is that Guido once told me, after I asked him to cut down a newly installed tip, "Well, OK. But you do know the magic of these tips are in the top layers."
It didn't occur to me at the time to even consider he was being serious and/or that the top layers might be different from the bottom layers but when I got home I started wondering why "the bottom" of these tips were so identified. I mean, there must be a reason for that, right? So just to be on the safe side I install them upside down

Lou Figueroa