Too much airflow is bad, that's why we use rheostats on our fans, better control over air flow.
Too little air flow is worse
We have our incubators set up with a false wall hiding the heat tape from the inside of the incubator.
Our fan sucks air downwards and blows into the false wall and the air moves across the heat tape and upwards to the top of the incubator and out into the incubator to be pulled down by the fan again...