I was thinking about buying a previous generation iPod Nano that's brand new and unused. But I'm concerned that even if unused, age alone can deteriorate lithium battery ability to hold a charge. So if buying a new unused 5th generation Nano (2009), that would make the battery 8 years old. Can I expect that Nano's battery to be as robust as a new 2015 7th generation Nano? In other words, can age in addition to usage deteriorate these batteries?