I’ve thru-hiked the A.T. twice in sandals (Tevas). I can’t report on the Keen’s, but here are some of my observations about hiking long distance trails in sandals:
(1) They’re ideal when it comes to comfort, expense, and wet conditions.
(2) When its cold, neoprene socks work well (Campmor sells them). When its really cold - lots of snow, etc. - wet suit booties work great. (used the sandal/wet suit booties combo in the high Sierra on PCT thru-hikes)
(3) Too much ventilation can be a problem after a few hundred miles (cracking in the heels is normally the first indication of this issue). This can be resolved by wearing socks & by carrying a bit of “bag balm” which works great on dry cracked skin.
Many hikers have completed the A.T. wearing sandals. I finished a hike with a guy who hiked in flip-flops in '04 and I know of at least 4 thru-hikers that have hiked the Trail barefoot!
Happpy Trails!
freebird