Contax N lens rebates



As you know, there are some pretty hefty rebates on Contax N lenses right now, until 8/31. Earlier on, the last date for the rebates was mentioned as 7/31 and then it got extended to 8/31. Does anyone know what time of the year these rebates are offered? Are they offered every year and is it possible that the last date will be extended again? With Canon, you can be reasonably sure of their rebate period and you can time the purchase of your lenses accordingly (though their rebates arent as huge). Is it the same way with Contax?