How should long-term investors think about cash drag versus optionality.?

Cash is often described as a drag on long-term returns, especially during extended bull markets. At the same time, holding cash provides optionality: the ability to rebalance, deploy capital during drawdowns, or reduce forced selling during periods of stress.

From a portfolio construction perspective, this creates an interesting tradeoff. Staying fully invested maximizes expected returns, but eliminates flexibility. Holding cash reduces expected returns, but may improve risk-adjusted outcomes depending on how and when it is deployed. How do you evaluate this tradeoff in practice? Do you treat cash as part of your defensive allocation, ignore it entirely, or adjust it based on market conditions? What framework has worked best for you over long cycles.?