Yate Loons are popular because they are cheap and their blade design can make them very quiet if running under 1000RPM.
The problem is that not all Yate Loons are the same.See this Yate Loon roundupPicture of the fan motors showing why they test different
Basically, looks as if some are "cheapened" versions and have smaller motors but the same fan blades. Besides sometimes having better sound qualities, the better ones will outlast the cheaper ones. I've had some of the cheaper ones last only a few months before the motor started rattling, but it is not unknown for the better ones to last quite a bit longer as long as you blow the dust out periodically.