I don't think it matters whether or not you're using OO. I think each function needs to do one particular task. If a subset of that task is needed by another task, then that subset needs to be factored out into a seperate function so that that code is unified for all consumers of that code.

Let's generalize the long loop code issue and say that any block (for languages that have them) that extends beyond some arbitrary length limit particularly if it has many nested blocks should have it's guts factored out.