Of those investors, way too many keep making the same mistakes over and over again -- mistakes that could easily reduce the value of their 401(k) plans.
What's worse, the list of mistakes goes on and on.
"From failing to take advantage of matched contributions to hidden fees that add up, there is more to a 401(k) than saving money," says Nicole Mayer, a financial adviser at RPG Life Transition Specialists.
The worst of the bunch are the ones that can really curb your savings, Mayer says. Here is her list of top mistakes that threaten the financial future of millions of 401(k) savers:
Failing to consider an IRA: "Leaving money in a former employer's 401(k) could add up to thousands of dollars in administrative fees over the long term," Mayer says. "Shifting the savings to an IRA will not only provide a diversified range of investment funds; it is less expensive than those that are actively managed."
Ignoring a matching offer: On the other hand, if a current employer offers to match 401(k) contributions of up to a certain sum, it would be a mistake to not leverage that benefit. "Most employers will match a percentage of your contributions into their employee's accounts," she says.
Becoming too conservative too soon: As retirement approaches, 401(k) investors may be tempted to reduce risk by limiting their plan's stock exposure. "Many investors fail to account for the fact that they will live another 25 years or more," Mayer says. "They will either need to alter their lifestyle or grow their portfolio."
Forgetting to rebalance: Rebalancing a 401(k) on an annual or semi-annual basis is a must. "Actively managing how savings are divided will prevent funds from becoming one-sided, which could spell trouble for when it is time to withdraw money," she says.
Relying on company stock: if you're offered company stock as part of your compensation, that's often a big help to your retirement plan. Just don't overweight your plan with company stock. If the stock goes south, it could take your retirement savings with it.
Avoid those land mines with your 401(k) and maximize the value of your retirement fund -- and keep your fund assets from blowing up.