Multirotor motor durability / continuous used as fan?

[sam1275]

Hello everyone, I have an idea of using multirotor motor as a fan, because it's small, brushless, very powerful, and good at controlling the speed, but I have a few questions about this:
1. Is it OK to use them as a long-term powered fan? Most multirotors will fly for just 10-20 minutes and have a rest, so will it shorten the life if I power it on for a few hours without stopping, or even 24*7?
2. If it's fine to run them continuously, then what is the MTBF of a good motor, such as DJI or so? I cannot find this specification online.
Thank you for any helping!

[mzzj]

Bearings are usually the weakest link and those can last anything between 0.1 and 10000 hours. This is also depends how well your prop is balanced.
I wouldn't use  for anything even partly critical.

[BradC]

1. Is it OK to use them as a long-term powered fan? Most multirotors will fly for just 10-20 minutes and have a rest, so will it shorten the life if I power it on for a few hours without stopping, or even 24*7?

No. Those motors are designed for intermittent use and will just smoke up and die if you run them continuously. There is no ventilation and the bearings are too small to conduct any heat away from the armature/commutator.
I've got several heli's (both multi and single rotor) and I killed my first one by flying it back to back with several batteries in a row. Now I have several of each model and rotate them and the batteries. This allows the motors time to cool down between runs.

[sam1275]

Thank you everyone!

[ivan747]

Well, they are burshless 
Doesn't take that much to try one. You should put the prop so that it directs airflow into the motor, and use a prop that actually blows air to the motor.
Put the ESC in the way as well.
And of course, derate the motor a lot.

Tell me about the results because I'm curious 

[BradC]

Well, they are burshless 

My bad. I missed that entirely. All mine are brushed and its the brushes that are the weak point.