I use Pelican 5150 cases and large amounts of rechargeable silica gel. I have not had any issues for four years on long term living assignments in the tropics in very wet environments. With that said, my 100-400 f4/5.6L lens is about to go in for it's very first cleaning. It's probably more an issue with a design of the lens and extreme environments rather than my fungus-beating strategy.
Noah