On a logo project, revisions are always the biggest variable. Sometimes it's a hole in one, and the first draft is the only draft. Sometimes we have to go back to the drawing board four or even five times. The average is two, and that's what we usually recommend when we estimate a logo project. If we end up needing more rounds of revision than we estimated, of course we're happy to do it, but it can push deadlines and increase costs.
The biggest factor in how many revisions you'll need is usually how many people you have reviewing. If your organization is led by a single decision-maker, and we can work directly with that person, we can usually assure a quick process. If you have a large board (or more than one board) that needs to weigh in, things get more complicated. We recommend keeping your circle of reviewers as small as possible, and involving them as early as possible, ideally in our initial meeting to outline the creative brief.