IRS Publication 970 does not state any limits apply to the exception regarding 529 plans and Service Academies. Just because there is no stated limit, does not mean that the IRS could apply one 20 years from now.
Here is the excerpt from IRS Pub. 970: (italics and bold face are mine).
Additional Tax on Taxable Distributions Generally, if you receive a taxable distribution, you must also pay a 10% additional tax on the amount included in income.
Exceptions. The 10% additional tax doesn't apply to the following distributions.
- 1. Paid to a beneficiary (or to the estate of the designated beneficiary) on or after the death of the designated beneficiary.
- 2. Made because the designated beneficiary is disabled. A person is considered to be disabled if he or she shows proof that he or she can't do any substantial gainful activity because of his or her physical or mental condition. A physician must determine that his or her condition can be expected to result in death or to be of long-continued and indefinite duration.
- 3. Included in income because the designated beneficiary received: a. A tax-free scholarship or fellowship grant (see Tax-Free Scholarships and Fellowship Grants in chapter 1); b. Veterans' educational assistance (see Veterans' Benefits in chapter 1); c. Employer-provided educational assistance (see chapter 10); or d. Any other nontaxable (tax-free) payments (other than gifts or inheritances) received as educational assistance. This exception applies only to the extent the distribution isn't more than the scholarship, allowance, or payment.
- 4. Made on account of the attendance of the designated beneficiary at a U.S. military academy (such as the USMA at West Point). This exception applies only to the extent that the amount of the distribution doesn't exceed the costs of advanced education (as defined in section 2005(d)(3) of title 10 of the U.S. Code) attributable to such attendance.
- 5. Included in income only because the qualified education expenses were taken into account in determining the American opportunity or lifetime learning credit (see Coordination With American Opportunity and Lifetime Learning Credits, earlier).
- 6. Made before June 1, 2022, of an excess 2021 contribution (and any earnings on it). The distributed earnings must be included in gross income for the year in which the excess contribution was made.