• "Super savers" either contribute 15% of their pay or at least $17,550 to their 401(k) account, according to a study.
• The three top habits used all reduce the likelihood of paying unnecessary fees or interest.
• The practices that are relied on the least are nevertheless still good financial habits.

You may assume that people who save a boatload for retirement also do all the other things that financial experts recommend.

Not necessarily.

There are some good financial habits that such "super savers" are likely to rely on and others that appear less important to them, according to a study from Principal Financial Group.

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The company defines super savers as workers who put at least $17,550 in their 401(k) account — which is 90% of the contribution maximum of $19,500 — or contribute at least 15% of their pay. Principal's report is based on a survey of about 1,400 individuals ages 19 to 56 — with salaries ranging from under $35,000 to more than $250,000 — who meet that qualification.

When it comes to financial habits, 85% of super savers said they pay their bills on time, 73% pay their credit cards in full and 70% do not overdraw their checking account. All three of these habits avoid fees or interest that end up reducing cash available for other uses.

"A penny saved is a penny earned has never been truer, especially when it is saved on ancillary fees that aren't necessary if you are just careful," said Sri Reddy, senior vice president of retirement and income solutions at Principal.

Meanwhile, many of the super savers also appear to be going it alone: Fewer than half (44%) say they have a financial plan.

As far as the less-used habits go, just 21% say they follow a budget every month and 23% say they have a debt-payoff strategy. Less than a third spend time every month learning more about finances and investments.

Nevertheless, this shouldn't be a deterrent to others to practice these good habits, Reddy said.

"If you are just starting out in your savings journey, learning to budget, getting advice on finances and building strategies are great places to begin," Reddy said.

"The 'super savers' in the survey are generally those who have already taken action and have a good sense of their financial situations including prioritizing the minimization of debt," he said.