I'm approaching the process like this:
We are not bulk-converting anything, ever. We're doing a 'convert-on-touch' model where each individual post/article/page gets converted only when we actually touch it, one at a time. (Which makes sense, as some older layouts break during conversion and there could be any number of layout problems with any of them!)
But it is also possible that, with this strategy, I will end up having to redo one or two pages on a particular project because a layout didn't translate well or work the same. So it will require a rewrite at the very least. But I like the process more and more as we continue to move through the old posts.
So yeah. There may be some extra effort for me. But there is a reason why we are not mass converting posts. It's better for the client and I like where this is heading and the process I am using.