Retail investors looking to build long-term wealth should consider sticking to Systematic Investment Plans (SIPs) for a period of 5-7 years, recommended investment expert Girirajan Murugan. SIPs provide a disciplined approach to investing in mutual funds, allowing investors to pool their money and invest regularly in a systematic manner. By investing fixed amounts at regular intervals, investors can take advantage of market volatility and potentially earn higher returns over a longer time horizon. Murugan emphasized the importance of enduring short-term market fluctuations and maintaining a consistent investment strategy in order to accumulate substantial wealth over time.