Hm... yes, battlefields of Heaven is a little strange. Then again, if angels can lay siege to Hell, who says demons can't lay siege to Heaven. Maybe there is fighting going on at the fringes of Heaven. But then, who'd be protecting the borders now if that were the case.
There is just so much we don't know. And that can make it very difficult to speculate.

How fast time goes by in Heaven is another one of those things.

On the one hand it's nice to have so much room for headcanon, on the other I'd really wish we'd get a few more answers in canon.