- If retirement finds me superhealthy, then I might not be able to spend all of that HSA money. In that case, it would go to my heirs

Once you reach 65, you can withdraw the money for any purpose if you are willing to pay ordinary income tax on it, just like an IRA or 401(k). Any money withdrawn for medical purposes is still tax free.

I am considering my HSA as a combo medical savings and 401(k)/IRA supplement. So far, I am covering all my medical costs out of my pocket and not withdrawing from my HSA. Of course, I've been pretty healthy, and my medical insurance covers any 'preventive care' at 100%, so my out of pocket expenses thus far have been nothing.

- The HSA fund investment options are limited to what the HSA plan adminstrator allows.

Yes, and the fees can be expensive. Until my HSA is funded to a level where the fees are less onerous as a % of the account balance, I am just keeping my HSA in a savings account that was earning almost 5% - it's dropped a bit since the Fed dropped rates, but is still nearly 4.5%. Once I get 3 years contributions or so, so I get closer to $10k, I will look to roll the money over to something where it can be invested in the market.

AJ