Yes, if you serious about your preparations, then you must go for the old papers. Before every fight, a lot of research about the enemy has to be done. This research takes lots of efforts, but in the end, the results will amaze you. same is the case with the exams, to crack IIT JAM exam, you must practice the IIT JAM Question Papers. By solving these, you will get to know the difficulty level and also the type of questions asked in the examination. Solving these also will help you in analyzing yourself and by practising, you can enhance your speed and accuracy as well.