Hard to say except they are cheap and nice quality. They have sleeved bearing instead of reall ball bearings. They might only last a year on continuos use in a blowing up/ down configuration, might last longer. They should last a LOT longer at the horizonal setup. My Yate Loon mediums are at 1.5 years horizontal and are awesome, no low-speed undervolted clicking etc that plauge some other fans.
There are better fans. I could take the time to link fan tests by real users but too much work. You'll need to PM me for that. Meaning ya really wanna know and are dedicated and not a post once in a blue moon just for input. Tired of the sponges ya know?
They are quiet and blow good air with decent pressure ratings. Cheap too.
That said, there is a long standing issue with it seems fake Yate Loons. The only USA distributor lots of us know about that sell ONLY yate Loons direct from the manufacturere is Petras. Here is the latest fiasco, good testing and detective work. Darn recent post too, last time this came up was almost 2 years ago, we all thought it was solved.