I save them whenever I get them... There are two types, plain and indicating. The indicating turn blue when they're moist, and cost a bit more. You can dry them out in the oven.
I'd like to find a supply of cheap bulk silica locally... You know it must be cheap in bulk. Mostly to make larger packs for longer term storage, larger items, etc. I've been trying to think of an ideal local vendor who gets an excess of them and maybe saves them.... Like computer vendors who build machines? Or maybe someone in mfg who buys them by the ton for next to nothing.
One gotcha with silica is that it works best when maintaining dryness in a stable, enclosed environment because it takes quite a while to absorb the moisture. So if gear gets wet and put in the bag, or the bag gets wet, there is still a very significant risk.
And I forgot to mention earlier that the fungus damage can be permanent and etches glass and glass coatings. A lot of lenses on ebay have fungus issues, even those that otherwise look mint.