If you concentrating to gain only on the theoretical knowledge of SQL Server, I would say 12 month is good enough. But, becoming an MCSA is not only about memorizing the concepts, its about implementing the right concept at the right place.SQL Server is like a platter, its serves you with all variety of dishes, but the onus to bring out the uniqueness depends on individual.Having said that, I would re-iterate, what I have read and have understood from the past few years into SQL Server,even if you do not have a job, try to do things voluntarily, these along with your studies would provide you with much wider landscape, which I think any future employeer would not like to miss.

All the very best and God speed.