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It is argued that just as relationships are said to face a "seven-year itch," scientific and technical subjects encounter a five-year itch. Five years is roughly the period during which you can master and contribute significantly to a subject. Beyond that, there are still many things to investigate, but the point is that you won’t discover them. After five years, some degree of tunnel vision is almost guaranteed. Managers face a similar time span. A fresh topic, with a different set of challenges and boundary conditions, allows you to contribute to a new field and broaden your skills. An engineer or scientist with expertise in different corners of microelectronic design is able to bring more value to a company or a research team. Moreover, a regular change of topic keeps your mind fresh and eager for challenges.