I gave CFAI 2011 mock. I took around 2 hr and 40 minutes. It was more than the scweser mocks which i finish in around 2 hr 15 minutes
CFAI mocks have little traps in the options, so need to double check the answers.
I guess if a candidate is well prepared, then it should not take more than two and half hours, Because u need atleast need 30 minutes to go through the questions which you are not confident of
I can usually tell which questions are going to take a long time to answer (based on how many calculations are required, and how confused I am), and skip those if I want to gain some ground, time-wise.