I used one of those savings plans for medical issues. The rules were that I had to spend it all by the end of the year or lose my money. It worked well until I quit my job. I didn’t know that I could not use it after the day I resigned or I would have went on a medical spending spree. I ended up losing over 500 dollars. I won’t touch them now.
The particular plan you were in sucks - you have to guess your future medical expenses pretty closely in order to benefit from it. However, there is the medical savings account, allowed when using a high-deductible medical insurance plan, that is pretty advantageous; you can accumulate savings over the years - of course little or no interest is paid, but contributions are before tax, and medical expenditures incur no tax liability.