Hey there

If you have time and interest you should definitely and many students do so. The level of questions are same as of JEE advance so you can prepare for olympiads too. It is seen that those who prepare for JEE crack olympiads more easily due to similarity in difficulty level. But if you want to focus only on JEE then you can do that too it will save your time and energy and you will have edge over others.

Good luck