Use the 1st Gen iPhone as a spare?

Being the curious person that I am, I wanted to see if I could use my iPhone 1st Gen as an emergency backup for my iPhone 3G. At least with AT&T I was not able to do it, without having to sync to iTunes. But alas, no dice. You cannot do this without reactivating the iPhone with AT&T. And, well I’m not going to be doing that. Just something for everybody to think about, if you were possibly thinking about doing that. I might call AT&T to see if there is anything that can be done, like register both and be able to switch between the two. If I get anywhere I’ll report back.