It really depends on a number of factors, one of which is your understanding of the test and requirements of the band scores. If your English is suitable for the band score you are aiming for, you will only need to focus on exam skills to make sure you reach your potential. The skills will help you understand how to approach questions and what the examiner is looking for in your writing and speaking. Once you feel comfortable with all that, you will have a clear idea of how long you want to practice before your test. Whatever you decide, make sure you are frequently getting the band score you want in practice tests.
All the best
Because of my wide range of interests, I have not yet decided what career path to follow into the future. In the short run, I hope to study abroad for a year, in the process immersing myself in another culture, and deepening my personal and academic understanding of international affairs. After studying abroad, my options would include working for a nonprofit organization, entering the corporate world, and attending law school. In the long run, I envision for myself a career straddling the highest levels of international relations, politics, and business. I could achieve this admittedly ambitious goal by advancing within a nonprofit group, think tank, or major international company. Perhaps most appealingly, I could also achieve this goal by entering public service and obtaining some degree of influence over actual foreign policy decisions -— that is, becoming a player myself in the real-life game of Diplomacy.