for the people that run fans inside of your incubator do you keep them hooked up to the thermostat so they turn on and off with the heat or do your fans run 24/7?

Always ran mine 24/7

24/7

24/7
the whole idea for the fans are to mix the air temps.
If you want that nice even temp all over the incubator.
Then I would run them all the time.

24/7

24/7
But remember some fan's will run at a higher rpm and push more air around than you want. If that is the case you may want to run it through a dimmer switch to lower the rpm's.

for the people that run fans inside of your incubator do you keep them hooked up to the thermostat so they turn on and off with the heat or do your fans run 24/7?

No . They run all the time .

All the time, if you cycle it the thermal gradient between shelves is to extreme. I have also found that the fan should be mounted horizontal and not vertical. I have done a few mini-fridge mods. I don't know how one would work in a full size fridge.