Questions about upgrading to digital phone service

I've received lots of letters (and finally an email) about upgrading to digital phone service. Am I one of the last who hasn't upgraded yet or are there others who also haven't done it yet? Right now, I can have more than 2 different phones hooked up, but my understanding is that with the new eMTA or WiFi modem, I can only have 2. Is that correct? I think they should also be within a short distance from each other, not on 2 different floors. Is it even possible to get hooked up with more than 2 voice ports using the new digital equipment options? Also, how long do the batteries last? Thanks!