In my experience, they are not accurate at all!! After the new pomme vernis color came out, I went into the store to put myself on the waitlist for the Roxbury Drive. The SA took down my name and information and said they'd call me as soon as they got one in. That was two months ago, no phone call. The other day, I went in to check out some purses, and I saw one on the display!! Nice customer service, Louis!!
Here it seems to also depend on how much you spend at the store and how important you are to the store.
You can be first on the waitlist for months but it doesn't mean anything if a VIP wants the same item.