Well, as someone's signature said (sorry, i forget whose): "in theory practice and theory are the same. In practice they are not"
In theory, you have a point. However the 30-fold increase in battery life is hard to believe. If it turned out to be true, someone on nokia is going to at least get a pay cut (maybe a 100% one, if you get what i mean) for missing this
What is needed here is practical testing: don't use wi-fi at all and see how much the battery lasts. I'm betting no more than 3-4 days, since that's what my dumb sony ericsson gets (admittedly on a smaller battery, but not much)