I think your plan misunderstands the present value vs future value of money. Let's assume the tax laws and the economy stay more or less the same. You contribute $1000 in the HSA and you have a $1000 expense today.
If you delay the reimbursement for 30 years, that $1000 in the HSA is likely to grow to around $10,000 (if you have it invested in a market index fund and the market makes 8%). You can withdraw $1000 as a completely tax-free reimbursement to yourself, but you will pay regular income tax to withdraw the other $9000. Assuming tax rates around 25%, you get $6750, plus the $1000. In other words, you invested $1000 plus paid a $1000 medical bill in 2025, for a return of $7750 in 30 years, that's a return of only 4.5% per year.
However, if you contribute $1000, and reimburse yourself right away, you have $220 of tax savings, plus the $1000 you don't have to pay to the provider. If you invest that $1220 in a Roth IRA at a market average of 8%, you will have $13,341 in 30 years. Twice as much money as your delayed reimbursement scheme.
If you are maxed out on both your Roth 401k and Roth IRA contributions, you can invest the money in stocks, and pay 15% long term capital gains tax instead of 25% or more regular income tax (again, assuming the laws stay the same), ending up with $11,300, which is a 45% higher return than your delayed reimbursement scheme (assuming you have the ability to invest your tax savings and your medical costs instead of spending it on other things.)
