How do you balance simplicity and flexibility when planning for long-term financial independence?

When planning for financial independence, portfolios are often evaluated not just on expected returns, but on how reliably they support spending across different market environments. Concepts like sequence-of-returns risk, withdrawal flexibility, and behavioral sustainability tend to matter more as the timeline shortens.

On one hand, staying fully invested maximizes long-term expected returns and keeps the strategy simple. On the other hand, some level of flexibility such as cash buffers or lower-volatility assets can reduce forced selling during downturns and provide room to adjust spending when markets are stressed.

I’m curious how others here think about this tradeoff from an FI perspective. How do you decide when added flexibility meaningfully improves sustainability versus when it just adds unnecessary drag or complexity? And how does that decision change as you move closer to, or into, the withdrawal phase?

Not looking for specific fund recommendations more interested in frameworks and principles that have held up across full cycles.