As Congress reconsiders various tax breaks it voted into existence (home mortgage deductions, etc.), could 529s college savings plans, which have exploded in popularity in the past five years, come in for increased scrutiny and possible elimination?

According to a recent report by the United States Government Accountability Office, the revenue lost due to 529-related tax breaks – which include capital gains tax, and estate and gift taxes that are avoided as a result of the use of 529s as an estate planning tool - was an estimated $1.6 billion in fiscal year 2011 alone. In its report, the GAO reiterates its previous recommendation to Congress that it revisit tax expenditures like those from 529 plans from time to time. “We have recommended in the past that tax expenditures be periodically reviewed to determine their effectiveness in achieving specific policy goals, particularly given the nation’s long-term fiscal imbalance,” the report says.

Experts agree that advisors needn’t worry any time soon. The 529s are about as permanent a fixture on the list of tax exemptions as any of them. A few factors are contributing to that status. The plans are great PR for state officials who aren’t likely to give them up without a fight. Government web sites typically tout their “commitment to education” demonstrated by their continued support of their state’s 529 plan (see the web site of West Virginia’s Treasurer, John Perdue, for an excellent example.)

Most importantly, they’re widely used by individuals across all income levels: A 2012 survey by the College Savings Foundation found that 30% of families whose children are college-bound had a 529 account. And as John Hurley, who bills himself as the “529 Guru,” notes on his website, most members of Congress no doubt themselves invest in 529s for their children and grandchildren. Most importantly perhaps, President Obama and the First Lady have made “very large contributions” to 529 plans, naming their daughters, Malia and Sasha, as beneficiaries.