When just starting a grow room how often to run fans and filters with lights or 24/7

I've heard that all the fans an other goodies are only necessary when plants are in bloom

I run fans 24/7 in veg . fights power mildew and promotes stronger stems . and also 24/7 in flower obsoleting fans. you can turn off fans that cool the lights. and the carbon filter most people just hook them to light cooling fans run them 12/12 run your fans 24/7 don't chance mold .

I run the exhaust fans during lights on, only...
... and I let the small fan run all the time, stirring the air inside the closet.

Somebody is giving you bad advise.