Ive been using my Oly DSLR for about 4yrs running. Used this in the most extreme environtments ever (too hot, too cold, too dry, too humid, too wet). I keep it safe from the elements either inside my camera bag or inside the camerabag placed inside a drybag, if its too wet or too sandy or too cold. And i've never forget to do proper mainteneace after each use before storage. I've never tried using a drybox. And even then, my camera and lens still remains fresh, without any fungal or mildew growth.
And recently i bought a 2ndhand lens online, this one with small fungal growth inside the front lens element. The previous owner told me that this happened because he rarely used the lens, eventhough he kept it well inside, dry and comfy..
In summary, if you rarely use your lens / camera. Sooner or later, it will degenarate and would breed fungus and molds. But if you use them regularly, even at the worst conditions (with proper maitenance, of course), this will inhibit floral growth.