I have some Glacern CAT 40 tool holders and some from Mari Tool. All are about 2 years old now. Two of five Glacern ones are showing a bit of fretting on the taper. The Mari ones don't show any wear yet (I have nine of those). I actually have larger tools and thus take heavier cuts with tools in the Mari ones. One of the Mari ones did get a little flash rust on the taper from me holding it in my hand on a very hot day, but it cleaned right up with scotch brite. The Glacern holder that shows the most wear is an integral CAT 40/drill chuck which I find odd since it should not see any appreciable side loading.
Hercules
2008 TM-1, 2008 TL-3, 2009 TL-1, 2010 VF-2YT