In my experience the date you receive your back pay has a lot to do with the company you work for. It also has to do with the length of time you were off from work, and the rate at which your company handles paperwork. I've read of former employees waiting anywhere from months to years for their backpay. But, the sooner you file the claim, and the more you push for your backpay, the sooner you will recieve it.

Of course, if you're working for AIG I wouldn't expect anything anytime soon.