Well... I have a bunch of fans. My exhaust fan runs almost always at some speed.
I use fans to move air, but also to alliviate pockets of moisture or fix hot spots. They are on smart plugs, some run minutes, some hours, but if you saw it you'd think it was a random thing of fans on and off!
But it works. And I like the smart controls and using ifttt and alexa and Google home.
To be more specific in answering you, run the exhaust when humidity is high or temps over 75f. Which is almost always. When temp falls humidity rises, those numbers are a good start to dialing things in.
Next, CFM. You want your air changed often. Lots of factors here, but I find more is better than less.
That takes care of air out. So, air in is next. You want as much coming in as going out. To do this, you can use fans, or open vents or flaps... But that is a must. I like math and numbers, but basically, zip it up, turn out and in fans on. If tent sucks in - you need more. If it puffs out, less.
The "air in" is most of the problem. If it's hot, cold, dry, humid, it matters. I have found the dehumidifier the most valuable piece of equipment I have for environment. Drier air works better. Even if you want to have 65% rh, start the air coming in at 43%.
My room the tents are in is kept at 73f, with 43% rh. I bring this into my tents with an intake fan (a fan blowing into tent) that is 1/2 the cpm of the exhaust. The other 1/2 is in how I'm running both tents on one fan and some math.
Anyway, more or less, you'll most always have some fan running. And more than not, more than 1