IRS rules and regulations allow account holders to reimburse themselves with HSA funds for a qualified out-of-pocket medical expense, as long as they are eligible. That means they can do it today, tomorrow, or 20 years from now.1 The only requirements are that the account holder had the HSA established at the time the expense was incurred (date of service)2 and that the expense was not reimbursed in any other way.
1. “Internal Revenue Bulletin: 2004-2: III. Contributions to HSAs. Q-24. When is an Individual Permitted to Receive Distributions from an HSA?” Internal Revenue Service, January 12, 2004. https://www.irs.gov/irb/2004-02_IRB.
2. “§ 262; 1.262-1. Medical, Dental, Etc., Expenses.” Internal Revenue Service. https://www.irs.gov/pub/irs-drop/rr-99-28.pdf.