Midyear 401(k) Checkup: 3 Things To Do Before the Summer Ends by Martha C. White With the stock market hitting record highs and summer in full swing, it can be easy to forget your 401(k). But if you want to maximize your gains, investing experts say there are a few moves you should make before Labor Day. According to Fidelity Investments, the average 401(k) balance was $103,700 as of the first quarter, an 8% increase over the previous quarter.