Students take it casually on solving the previous Year papers for JEE Mains or 2-3 Years previous years paper i.e. Previous year papers for JEE Main Jan 2019, Previous year papers for JEE Main April 2019 and many more. Students forget that solving previous year paper questions is the most important part of JEE preparation. These questions must be solved to get a good rank in JEE and hey! Who told you that IIT does not repeat questions? Let's look at this point from both mains and advanced point of view -
JEE Mains- Some previous year JEE advanced questions repeats as it in mains. Apart from this in the chemistry section you will find some reactions repeating after every 4–5 years (of course question would not exactly be same). In maths and physics also, questions do repeat. So previous year questions must be solved for JEE mains.
JEE advanced- Question do not exactly repeat but from past 2–3 years some questions are repeating in maths. In chemistry also you will find some previous year questions in options of more than one correct type questions.
So, it’s important to check at least last 4-5 papers.