You own the money in your HSA and it does not expire. Should you change jobs or health care coverage during the year you will not lose the money in your Health Savings Account. The money you contribute is your money until you spend it, for the rest of your life.
Your Health Savings Account is portable and non-forfeitable. The money in your account may earn tax-free interest, and any money you don't spend continues to grow tax free until you use it. When you take money out of your Health Savings Account, you will not be taxed as long as you are paying for eligible expenses.