"Flexible spending accounts have always been an attractive option for those on employer-sponsored health plans. But one provision has traditionally soured the deal for some.FSAs “use it or lose it” rules have required enrollees to use all of the tax-free money they put into FSAs by the end of the year (sometimes with a grace period), or they lose the money. Many unnecessary pairs of glasses have been bought as consumers try to get something of value with their lingering account balances."