Past flights
Card benefit claims have to be filed within 20 to 100 days of the flight. Almost nobody knows that, so the money is usually gone before the receipts are. Here is what is still worth checking, and what honestly is not.
Still open
If the airline cancelled, or changed your flight significantly and you did not travel, the refund is owed under federal rules. There is no federal deadline on asking. Airlines rely on you not knowing that.
Still open
Anything issued and not yet used is still money, and most of it expires on a date nobody wrote down. We read the expiry out of the confirmation and remind you before it goes.
Still open
US carriers must refund the checked bag fee when a bag is materially delayed. Separate from any card benefit, and separately forgotten.
Usually closed
These are the big numbers, and they are also the ones that expire first: most windows are 60 days, some as short as 20. A flight from last year is past all of them. We will tell you that plainly rather than sending you to gather receipts for nothing.
The honest version: looking backwards finds refunds and forgotten credits. Looking forwards is where the card money is, because that is the only way to be inside a 60-day window when it matters.