That is an overly conservative approach that sacrifices a lot of growth for not much more safety. It also exposes you to inflation risk, which is a significant concern these days.

Most people in actual retirement I know do something like keep ~2 years of cash in short-term treasuries and everything else in equities. That gives you a lot of buffer to time-shift equity drawdown, which is the main risk with equities, while retaining almost all of the benefit of equities. Simple and relatively robust.