How long does dried tofu last in the tropics in a hot room?

I keep a metal storeroom in Thailand. Very little ventilation. There is no air-con, only humidity control. I have had disasters within a week of placing unopened miso in my unit in the hot season (huh, I thought the salt would preserve it!)

Both the packages of dried tofu that I bought in Japan and stashed for my return 7 months later have become discoloured – yellowish and a bit crumbly also. How can I avoid this in the future? Are some brands better packed, maybe vacuum-sealed? I am surprised they did not last especially because they were in a styrofoam cooler.

I basically give up stashing anything other than dried seaweed and dried mushrooms. Maybe tamari (which curipusly was very hard to find in Japan – seems to be much more popular in Canada, cheaper too)

Of course, Japanese groceries are available in Bangkok. But selection is so much better in Tokyo.