The DC motor "scandal" I have been following for awhile... just another way to make things more expensive and more prone to failure, while accomplishing nothing other than pulling a few less watts. Just money wasted with R&D, IMO.
You can get plenty of quiet and plenty of efficiency from 60 and 70 year old fans... I should know, I own some.
They are warrantied for 6 years rated 24/7
"Warranty" can often be taken as a dirty word, depending on the conditions behind it.
People won't maintenance(clean) the things, and no doubt they'll fail early, within a year or two, and then the warranty will be re-drafted to adjust to reality...