1. When I have given advance certification, I had set target for every week and followed it religiously.
2. For me, number of hours do not matter, I identified which all topic I am good at and what all topics were new to me. For example, I was confident of proc sql so I didnt spend much time on proc sql related topics and devoted more time to macros and other topics.
3. Its difficult to say how many months would it require but read certification guide atleast two times.