I'm on my fourth brokerage account for AA and Delta miles. I started with Schwab, them moved to Ameritrade and Waterhouse. All those miles posted fairly quickly. About three months ago, I moved to E-Trade. So far less than half the miles have posted, and I'm told the rest will appear after 6 months.
I referred my brother to receive a 2500 mile bonus, but was told his miles and the bonus won't post for 6 months because his is the referral account. The only cost has been $50 to close my account from Waterhouse.