I think the best answer to this question is both… The mock exams from Schweser as well as the CFA Institute are pretty good practice for the real test, at least in my experience. The CFA Institute has obviously got the upper hand in terms of knowing what is going to be tested on exam day, so I would probably go through the Schweser exams first and save the CFA Institute mock as the last prep before the actual test.
Running out of mock exams?
If you are running out of mock exams, I would recommend having a look at Wiley CFA Exam Review Products. They sell a standalone product with 1,500+ practice questions. To give you a sense about how many questions that is, there is “only” 1284 end of chapter questions in the entire curriculum. Based on the required exam pace of 1.5 minute per question (240 questions in 6 hours) it will take at least 37.5 hours to work your way through the Wiley practice questions. If we factor in a similar amount of time revising the answers you have got 2 extra full-time work weeks of question practice with this product. It is unlikely that you are going to need any more than that.
Practice the exam conditions:
I would also advice that you try and simulate the actual exam conditions as closely as possible when you practice your mock exams. Try and find a desk in a library or another quiet place where you can sit, and don’t bring your phone or anything else that will distract you, only bring the exact items that you are allowed to bring for the actual exam (pencil, eraser, watch & calculator) and obviously the mock test, and some paper to write your answers on. In this way you won’t be distracted by your TV, Facebook, YouTube, your friends or anything else. Ideally try and replicate the timing of the exam as well: morning session 09:00 – 12:00 and afternoon session 14:00 – 17:00. Having experienced the exam conditions on your own body will definitely improve your ability to structure your time come exam day, and it will provide a significant confidence boost, knowing that you are already familiar with the exam conditions. It is one thing to understand conceptually that you need to sit on a school bench for six hours solving multiple choice questions under time pressure; it is something quite different actually having done it several times.
A mock a month:
I generally recommend that mock exams should be attempted in the period immediately preceding the actual test. But if you do have the extra energy, reserving one day a month during the earlier stages of your study period to attempt a mock exam works brilliantly as well. In this way you maintain your focus on the end outcome that you are studying towards, and it also provides some cues about areas of strength and weakness, as you progress through the curriculum.
The final month before the exam:
During the final month before the exam I would recommend that you do a mock exam every Saturday replicating exam conditions as closely as possible, as described above. During the very last week prior to exam day I would recommend that you complete a mock exam every second day, leaving enough time in-between to revise your answers. It is crucial that you allow time for revising your answers having completed each mock exam. It is especially important that you focus on the questions that you have answered incorrectly, to really learn the concepts so you can answer a similar question confidently next time it pops up.