The only issue I have had with highly breathable hikers such as Merrill and Vasque other than the somewhat lower level of support is dirt. Fine dirt works its way into the boot and your socks and feet pick up a load. The fine powder found in the pockets of the red rock Utah country seems to be the worst. I carry an extra pair of socks (abave the normal extra) and use handi-wipes or water to keep toes clean, knock dirt out of socks, remove insoles and knock dirt out of shoes. Quick to do at break and makes for happy feet at end of day.