I submitted my purchase on September 26th, a Saturday by the way and I received the check today October 9th. 13 days after submission I received the check.
I submitted my Mobil 1 rebate request last weekend using their on line method. The system doesn't even yet recognize me as having submitted it. I'll give them another 2 weeks or so. If nothing by then I'll return the oil from where I got it and buy some Castrol Edge 0W-40 instead.
^This happened to me as well, but I got my two rebate checks in less than three weeks. I don't think their online system does a very good job with the status updates.