Meh, this sounds remarkably like my own plan, and that worked out fine.
It depends on whether what you need to work on is the content, or test-taking skills like timing. Most content review has passage-based practice problems, so really the only advantages to the actual practice tests are a) score prediction b) timing practice.
If timing isn't an issue (for some people it's not) and they don't have test-specific anxiety, I don't see why 2 weeks of practice tests wouldn't be enough. They'll get a score estimate out of it and can choose to defer if they're not ready. The score estimate wouldn't be accurate if they took the test before finishing content review, so no point in blowing tests earlier. And the test questions are usually easier than the content review practice questions anyway.