Originally Posted by randy6
A lens that is properly cared for will not get fungus. In addition, many lenses that are "diagnosed" with "fungus" have other issues such as lubricant haze, separation, or the blacking on the edges lifting up (Schneideritus). The best way to avoid fungus is to keep the lenses clean - no dirt equals no food, ergo no fungus. Fugus does not "eat" glass or coating.
A lens such as a double Gauss type with 8 air-glass surfaces, six of then internal, is a flare machine. Lubricant haze can and does build up over time, this is exacerbated by high temperatures and misguided efforts to clean/lube shutters (if the lens is mounted in a shutter). Just get coated lenses and take care of them, you'll have no problems.