ipod and iphone: keeping them in shape

while dumpster diving, someone i knew found a fully functioning iphone 3gs 8gb in the trash, so i jailbroke it, and it's quite fun. a few months later, i find a ipod 7th gen 160gb for $20 at a "vintage mall", and i'm getting quite hooked to it. usually these things don't go kaput like phat xbox 360s, but these things both use batteries and data storage, which are difficult to replace and can fail. i store these things in a cold, dark, dry place, and i don't have them on a charger constantly. is there anything else i can do to keep them functional while still using them somewhat frequently? i also found a galaxy s3, which doesn't spook me as much, because the battery is easy to replace, but idk about the data storage for the OS. if anyone either has experience with failure in these devices, or knows how to outright prevent failure as effectively as possible, let me know.