While the disposition effect has been widely documented among retail investors, its presence among long-term retirement investors remains unexplored, particularly among SMSF investors who manage their own retirement portfolios. Using the daily trading records of 1,651 SMSF accounts at a major Australian brokerage between 1995 to 2022, we test whether the disposition effect is prevalent among these investors and how it varies across investor life cycle circumstances. Our findings indicate that SMSF investors demonstrate disposition bias, but the effect is less pronounced than that among retail investors reported by prior studies. The bias disappears in June, suggesting that tax-motivated selling may take precedence at the end of the financial year. Investors in their pension phase display a stronger disposition effect than accumulation phase accounts, reflecting their high-risk aversion and short-term liquidity demands during retirement. The disposition effect cannot be attributed to portfolio rebalancing or short-term performance justification. Interestingly, in the long run, the stocks held at a loss tend to outperform the stocks sold at a gain. This contradicts the conventional notion that the disposition effect results in poorer portfolio performance. We also find that trading frequency and accumulated trading experience plays a critical role in reducing the disposition bias