Originally Posted by
LondonElite
Some countries (USA for example) do this while you get visas sorted out, or in order to avoid problems with visa stamps that are not universally welcomed (i.e. Israel). Many others countries don't allow this. It's weird, but it does happen.
Unless the US messes up, the US won't give an individual two ordinary US passports with concurrent validity that overlaps for seven years (or even more). It (7 year concurrent validity on ordinary US passports) just doesn't happen with US passports unless some mess-up hits.