Did you find what was causing your data connection to stay on line?
There's a couple of other culprits to add to my list above as well.
Nokia Drop can go onine without it actually showing up, if you're using that check its settings, also if you have a paid version of JoikuSpot installed you may also have Joiku News and this can also go online randomly if you have Logged in to Joiku News, it will not show up as an active app. When you check the Connection Manager you may see the App is shown as "xmppservice", if this is the case then it's something like one of these two apps accessing the data connection.
Nokia N9 Nokia E7 HP Touchpad Dell Inspiron 14z i5
I think it just took awhile to settle down to be honest. I wasn't exiting the mail application the correct way. I think it was as simple as that. I'm wary of widgets anyway, purely from a practical point of view. Other than email or texts/calls, I want to open applications if I want to check something, not having constantly refresshing. Mainly to preserve the battery for as long as possible!
Overall the phone seems fine. Things are little neater. I do miss the message preview though.