They succeed when you succeed. If you're considering graduate or professional school, find out early what exams you need to take to get into the program you want to be in. If you have options, find out which ones fit your needs. Check into internships or part-time jobs while you're still in school. When you continue your education is up to you.
Some students choose to work for a while and then to attend graduate school.
If you're considering postponing graduate school, or if you haven't decided whether it's right for you, contact the school you want to attend to see whether you should take your graduate exam now or wait until you're ready to enroll. Some schools accept only scores for tests taken within a certain period before enrollment. However, if that isn't an issue, it might be a good idea to take the test while everything you learned is still fresh. If you're looking for help in preparing for your graduate or professional exam, be sure to check out all the sample tests that are available. The test manufacturers offer study helps and practice tests to help test-takers prepare.