The only thing that might be an issue is the noise from a fan due to the location of the setup, if I can get the same level of cooling from a heat sink I think I'd rather do it silently.
I'm using a normal 80mm computer case fan (12V@0,02A) with a 7.5V AC adapter and I guarantee you that it is quite noiseless.
I'm just waiting for a power adapter for my hub and I'll put all my BE's next to the Ants in the same hub, and then, put them on a "shoe box" to properly manage the heat and create some tunneling to improve airflow and have it neatly arranged.
But let me ask you: besides the noise, have you already tried to use 0981 frequency and a fan? even for one hour.
That way you'd check if it is some heat issue or not.
And you might have some USB Hub lying around that you could use instead the extension cable?
These are just some ideas to troubleshoot your problem.