Comment by ghaff

That's a bit different. You're effectively getting "taxed" 100% on whatever is left over so you might as well spend the money on anything that has non-zero value to you.

But if you, say, only lost 30% or 50% of the balance, it's not immediately obvious if you should spend the balance or not.

OT but this is such a weird aspect of FSAs. I can carry some amount over with my plan which makes things a lot easier.