As of now there is no upper age limit for NEET because there is a case pending in the Supreme Court. Now we might have a judgment atleast the next year and if there is an upper age limit for NEET, you might miss out on it depending on your current age and the order of the Supreme Court. So it is always beneficial to appear for NEET in the same year that you are appearing for your 12th. That way you have an advantage.