Conventional wisdom suggests a Health Savings Account is best used as a retirement account for those who can afford it. Because a Health Savings Account affords you the opportunity to invest in equity mutual funds, financial products considered necessary to outpace inflation, and because health costs themselves continue to outpace inflation, I suggest individuals treat their Health Savings Account as a 401(k) and allow their health savings contributions to grow tax free by paying periodic doctor bills with after tax dollars. They should remember to keep all receipts however, and then use those old bills to withdraw funds at a future date after the investments in their Health Savings Account has had the opportunity to experience the miracle that is compound interest.
The fact remains, however, that most families cannot contribute $6,450 per year to a Health Savings Account and come out-of-pocket another $2,000 or more to cover dental bills, twisted ankles, and eye exams. For these families, I would advise them to allocate a portion of their Health Savings Account to the checking account or savings account deposit within the HSA, and invest whatever excess funds they do not estimate they will need this year into a investment account.
For example, suppose a family paid $1,750 in out-of-pocket expenses last year under their HDHP. In the next plan year, assuming no identified new expenses (braces, other elective surgery, etc), a family may want to place $2,000 into the HSA checking account feature and deposit the remaining balance into a blend of equity and bond mutual funds that can grow with the market. Keep in mind that the strategy here is to get ahead of spiraling health expenses, which are growing well above the rate of inflation.
No matter your financial situation, the first step is to make sure you have enough money in your HSA to cover your annual expenses and then, if you have additional money left over, to contribute as much as possible to an investment account and let it grow for years to come.