They won’t announce their intentions to run, until the very last moment possible.
The instant a candidate announces is the moment that the federal election commission and the election laws governing financing turn on. A candidate can posture and spend their money almost without limits before they are an officially declared candidate. One it’s official they are subject to spending limits and oversight. It would be stupid to not wait. Thus, I wouldn’t expect Mrs. Palin to declare her intentions until the day before the GOP convention.
The things you say are certainly worth considering. However, I am not sure how “the law” defines announcing. I remember in the past, candidates announcing several times, hoping to get a boost each time. I am not sure what makes it official.
Also, most debate forums will require that a candidate be announced. Palin can’t afford the heat she’s take for bypassing more than one or two debates. Fred Thompson tried that and was skewered by all of the others.