A thought .. since ethanol burns hotter than gasoline one would think engine temperatures being higher would weaken an engine over time and the duration of engine life would be lessened. Have you read any information regarding engine damage due to higher temperatures of ethanol based fuels?
Beyond my expertise, although lots of vehicles out in farm country have way over 100,000 miles on them with ethanol or higher ethanol blends. New flex-fuel engines aren’t a problem. Older engines definitely ARE a problem, but usually other stuff fails long before any heat damage might show up.