Well, I'm not him, but I'll weigh in - term limits on all civil service would probably be a good thing, and that includes changing roles/branches. Serving the country for a few years with passion and vigor is noble and heroic, but long term civil service risks stagnation, politicking, and corruption.

A Senator going out into the world to work on problems without government behind them would bolster their worldview. Perhaps after two terms in the Senate, a mandatory one or two terms off, then the Senator could run again. But definitely, lifetime politicians are a big potential problem. It certainly seems like they become more brazen and aristocratic over time.