The external power pack approach is fine for those times when you know you will be away from a source of recharging for a while.
But when the iPod/iPhone battery dies of old age, as they tend to do after two years or so, it's different. You have three options: throw it away and buy a new one (nice for Apple if the customer's happy to do that), pay whatever they ask to replace the battery (it isn't cheap), or try to do it yourself after buying a "special battery replacement kit".
Every other electronic device I've had allowed the battery to be removed and replaced - some very easily. Apple: not at all easy.
It's a pesky nuisance, because apart from that (and the early lousy reliability of the iPod), the product is excellent. Apple have a strange attitude to customers!