I strongly agree that maximizing HSA contributions - such as by making sure your spouse also has an HSA when 55 or over - is one of the best tax-advantaged accounts you can have. As Opus points out, the contributions are not taxed when they go into the HSA, and when spent on qualified medical expenses, they are not taxed when they come out of the HSA, unlike normal IRA distributions.
And everyone eventually has qualified medical expenses.
Younger taxpayers don't tend to think of this, but long-term care insurance can be a critical part of preserving one's retirement funds when getting older (and more ill). But the premiums for long-term care insurance are based on when you start paying for the insurance - the younger you are, the cheaper the premiums will be (allowing for inflation-driven increases).
These premiums can be deducted on Schedule A as a qualified medical expense (note that there is a separate limit for these premiums that must be applied), but since the Tax Cut and Jobs Act of 2017, 10% or fewer taxpayers are able to itemize their deductions by adding Schedule A to their return.
However, any qualified medical expense can be paid from an HSA, without regard to whether you itemize or not. And because your contributions to the HSA are not taxable, you in essence get a discount on paying those long-term care premiums.
Please note that the announced HSA contribution limits are as follows:
2019 – 3,500 – 7,000 - IRS Pub 969
2020 – 3,550 – 7,100 - IRS Rev. Proc 2019-25
2021 – 3,600 – 7,200 - IRS Rev. Proc 2020-32
In each case and for each year, the annual contribution limit for an HSA owned by a taxpayer who is 55 or older is increased by $1,000.