Most job descriptions don't change very often. Sometimes they will be updated to reflect changes in the company's needs or the employee's responsibilities. Other times, they may be completely rewritten to fit the current job market better. However, for the most part, job descriptions tend to stay relatively stable over time.
This stability is essential for both employers and employees. Employers need to rely on job descriptions to accurately reflect the duties and requirements of a given position. Similarly, employees need clear and consistent job descriptions to know their roles' expectations.
Of course, there are always exceptions to this rule. In some cases, jobs may frequently change due to the nature of the work. For example, employment in the tech industry is often very fluid and may require employees to adapt rapidly to new technologies. Similarly, jobs that are closely tied to current events may also change on a more frequent basis.
Overall, though, most job descriptions don't change very often. This stability can be beneficial for both employers and employees, as it provides a clear understanding of the expectations and requirements of a given role.