Financial experts offer these tips for long-term investors in 401(k) plans and other self-funded retirement accounts:

¢ Invest in mutual funds of stocks and bonds, including stock funds tied to broad market indexes such as the Standard & Poor’s 500 index of blue-chip companies. Over the long term, mutual funds have proven to be a reliable way to build wealth.

¢ Don’t concentrate assets in shares of one company, even if it is your employer. Many Enron Corp. employees saw their retirement savings wiped out when that company collapsed because they had all of their 401(k) assets in Enron stock.

¢ Gradually adjust your portfolio as you get older, shifting assets out of stock funds and into less-volatile bond funds and cash. One rule of thumb: Subtract your age from 100 and put that percentage in stocks. For a 60-year-old, that would be 40 percent in stocks and 60 percent in bonds.

¢ Consider investing in so-called target date mutual funds, which automatically adjust your portfolio as you age.