If you are intending to create more than 1 version of your mailing, working on the master version first will save you a lot of time. As well as general content, you can set important campaign level information (e.g. link tracking) in your master version so you only have to do it once. You can also set standard design elements, standard links (such as unsubscribe or homepage links) and data level personalisation (e.g. Dear %%First Name%%) which will then carry through to all other versions. Even if you need different links for different versions, you can often set the link structure just once in the master version.