[Rangerfan]

Hi ive been collecting many power rangers toys the last few weeks. I'm buying a lot off eBay since I missed out on so many older toys. Mostly morphers to begin with. I do get some with rotting battery compartments. This scare the crap out of me. But after I tried new batteries they still work. Some started out weak but finally came back on. So now I'm worried they can die out in the future. I display them now and I do click on the sounds here and there to keep the electronics moving.
So what is the main cause of the leaking batteries or rotten battery dust inside the compartments?

Is it from not using the electronics for years? If I used them will it prevent this?

Is it just long storage from the sellers which I believe it is. But now that I have the gunk inside already. I guess I can try to scrape the leakage dust of with a toothpick.