It is a crap shoot... Maybe I misunderstood what you were trying to say.
When you are searching for a coach, there are no guarantees about whether or not a candidate will improve your team or not. Obviously every AD thinks they have the second coming (or at least they should). In fact hiring a coach is probably one of the best examples of a crap shoot.
And if you mean AD's realize after 4 or 5 years they've screwed up... of course. But if you're saying they can see the future and know in the long term they are gonna to have a better program because of a hire they make, then I've got a bridge i'd like to sell you.
I agree an AD should have a vision for long term goals and should always BELIEVE they have a coach that will progress their teams, but the reality is they dont and will never know for sure.