I had the Love Jugs Mighty Mite fans on my bike just short of two years before one fan went out due to vibration. They sent me a free replacement fan, then I bought the frame mount kit. The fans and horn hardly even move at all now, even when sitting at idle. I've never had an issue with them falling off or coming loose.
Some of the fans mentioned I believe are more for rider comfort, such as the Harley fan, than actually cooling the heads down. Fans such as Wards and Love Jugs blow through a tunnel behind the spark plug for more of a cooling effect for the motor.
I don't care for how they look, but they blend in better after paint matching them to the motor. They 100% for a fact work. I used to bump down to 1 cylinder very easily on hot summer days when stuck in traffic. And that was when the bike was stock. Now a 124" at 11:1 compression, I've never bumped down to 1 cylinder with these fans on.