: If your existing balance is about to expire, buying the minimum amount of miles can reset the clock and save your entire stash. When to Avoid Buying

: If you are short by a few thousand miles for a specific, high-value redemption, buying a small amount to bridge the gap is often worth the premium.

: It is almost never worth buying miles for coach/economy seats, as the cash fare is typically lower than the cost of the miles needed.

: Some airlines (like Virgin Atlantic) charge high surcharges on award tickets, which can make a "free" flight more expensive than a cash ticket. How to Calculate the Value