I don't have any yet but I have heard legends [horror stories] about large Kaiju collections that have been stored for a long period of time and then developed mold. Is there anyway to prevent this? Does anyone have any experience in this field?

Yes, there is a cure...display them.

Don't store stuff in the basement or other areas that may have moisture.
Shouldn't be an issue in dry environments.

I don't have an answer about humidity and what role that may play...

Smoke a couple cigarettes in the room. It suffocates the mold spores.

Move to Arizona?

i think cedar blocks in the container might help, they absorb moisture, as well as deodorize. don't be cheap about the ones you get though, some are really crappy and require a sanding before they actually seem to do anything.

Get rid of any matangos

i've found a flamethrower works quite well to combat mold.

I almost want to lock this thread because I love it so much.

Pure skullbrain.

If you're worried about new stuff, I would worry more about them dissolving into a puddle of goo in 30 years than sprouting mold.

The old stuff was made from pretty cheap material, I think (relative to the new stuff). Some vintage pieces even have visible bubbling in the vinyl. Great little pockets for mold to take root. Consider also that vintage vinyl toys were probably dragged through the dirt by kids and never cleaned.

As for using desiccants to reduce environmental moisture, sure, why not. I've seen people with open tubs of the material in their display cases. Maybe someone knows where to find it?

If you feel like ponying up a little cash a dehumidifier would probably be best. In Japan they've also got these little plastic tubs that have some kind of chemical that absorbs water and then you just throw them out when the little tubs get full (after a couple of months). I honestly can't remember if they sell those in other countries, though, because I only bought them when I moved over here. Gotta do something in rainy season or EVERYTHING gets gross and smells mildewey.

Thanks for the advice guys. I don't have any moisture issues [yet] but my new place seems to be a lot hotter than my previous place [not just during the summer] and it had me a tad concerned about what the heat and possible moisture might do to my precious Kaiju. I will be going with the wood block // dehumidifier idea to protect my collection.

These should help...
http://www.desiccantpackets.com/