Portfolio Rebalancing

Annually or quarterly if you have time. When allocation drifts > 5% from target. Frequent rebalancing (monthly) has tax/trading costs; annual is common.

No, it locks in discipline and controls risk. Buy low, sell high naturally via rebalancing. Expected return same; volatility lower. Psychological benefit significant.

Trading fees, tax on gains if selling appreciated assets. In tax-deferred accounts (401k), costs zero. In taxable, consider tax-loss harvesting while rebalancing.