Hello user,
Sometimes it is helpfull to wait for next year jee exam after +2 boards and sometimes not .
If you have only aim to clear jee advanced you must b prepared well and preparation requires time.
I have seen some who had even failed jee even after waiting for one year!.
It also depends on you how much you’r focused on your goal, if you’r focused enough with rigourous practice daily I don’t think you need to wait for a whole year.
And if you’r going to wait then you must be produce better marks than before.
I must say that you first prepare for jee exams this year , see and analyse types of questions you can and cannot do! Re-practice question papers ,analyse your performance within a limited time daily keep a record and obviously keep revising the basics !!!!
Hope you do good!(Upvote the answer plz)