I think i wanna try something different from the iphone 4s when i go. $144 sounds way better than $220 for 2 4s's lol.
I too use my phone for EVERYTHING, all day too. So having a strong battery is important. My iPhone 4 has a pretty good battery, now but id like it to last longer. By the time october rolls around there will probably be a whole new series of phones out for me to choose from haha. Im definetly gunna shop the plans first though like you said, thats a good idea.