Oh come on! I have 30 year old TV eyepieces with no fungus. Don't put them away wet.
Being put away "dry" is no guarantee of safety.
I've had optical fungus attack:
- 35 Panoptic
- 2x PowerMate
- 17 ES92
All stored dry.
I received a 32mm Takahashi Abbe ortho brand new in box with optical fungus growing on the field lens.
These are the conditions in which fungus will grow:
- 65% humidity for at least 3 days
- Darkness
- Little to no airflow
- Source of nutrients (dust etc)
Here in New England during July, August, and September it's not uncommon for relative humidity during the day to be in the mid to high 70s (or even 80s) for days or weeks on-end.
If you put an eyepiece away dry but in a case where the RH in the case is 75%, then the environment is not actually dry even if there isn't any actual liquid condensation on the optics. If there are fungal spores on the surface, they can grow in that environment.
Ever since I've kept a hygrometer in the case and have been diligent about keeping fresh silica gel in the case, I haven't had any problems with fungus. Though some eyepiece caps can seal too tightly against the rubber eye cup and even if the case environment is dry, the environment around the lens is not, and it still runs the risk of fungus growing.