I'm getting a new series 3 watch today that will replace my 1st gen series 0. As this is my first replacement, I'm a bit confused. If I unpaid my old watch first, a backup is made that I can then use to set up my new watch. But since the iPhone can support multiple watches, I can also pair the new watch and keep the old one paired too. In both cases, I assume all my historical data is preserved (health and exercise). Is there any advantage of one method over the other and what differences are there. I imagine if I just add the new watch, it will be set up as new and need to be configured, which I don't mine. I just don't want to loose any data.