During the summer, even though only plumeria cuttings are in the "Everything Else" greenhouse and seedling are in the "Orchid" greenhouse, I have two fans running 24/7. During the winter, when these greenhouse are stacked to the gills with plants, I have 4 fans running, just not 24/7. I have often said, and I guess will continue doing so
, that air-movement is the single most neglected aspect when growing tropical plants. That may be true for all plants but all I grow are tropicals.