I applied for domicile October 2013, and recieved my certificate September 2014. The certificate expires in March 2015 and was approved in March 2014.
The system is ridiculous, and there is no actual need to have the Certificate in the first place. If a person has a Namibian Spouse, then they are automatically granted domicile by the very nature of the Namibian Constitution.
When I recieved my certificate, I was not told it was ready, a colleague saw the document at the Immigration office where I first applied, and subsequently told me it was there.
Maybe you should go to the office you applied at, they could have it there....
Mike