It's getting tiring for me, but SP's entry "timing" is not about me or us voters, it's about the "competition and their vetting process" and the "legal timeline".
If you think you might be supportive of a Palin candidacy, you still have ample time to finalize your decision. However, she will have to finalize her's a lot sooner than your own. So, be patient. Look at the field now, there's no one who can close the deal for most, so it's still totally open.
Here's a good article (by Mark America) that will provide some insight regarding the timing of the Palin entry....