Do we have to do the same thing every year?
That depends upon how satisfied you are with the results that you have gotten so far. Suppose that you assess your program and those results lead to new questions about your program? Well, you may want to assess the new questions that you have rather than do the same assessment all over again. On the other hand, there may be some aspects of the assessment process that you do want to do each year. Which approach you take depends upon how satisfied you are that the assessment has really answered your questions.
For example, imagine that in the first year of your assessment program, you assess or evaluate the quality of the research papers in your capstone seminar. You determine that, while they are generally competent, your students tend not to select the best research sources for their work. Your discussion about why this is so might lead to a number of conclusions: Perhaps at no point in the program does any course introduce students to methods of finding the best sources. You might decide to create a new course, insert a special module on research methods into an existing course, or review research methods in all courses of the major. Having done that, it might be appropriate to wait a year or two before assessing the seniors on this issue again so that all of them will have had a chance to learn better research methods.
But, in the meantime, you may want to assess some other aspect of the program, such as whether students can apply what they learn in class to real world problems, if that is one of the goals of your program. So, in year two, you assess that, rather than the quality of their research papers. Or you decide to focus upon their knowledge of specific content, if you have content goals for the students.
In short, you don't have to assess everything every year. Your key questions about your students will help you determine what you do want to assess each year.