You wouldn't put your entire 401(k) in one stock. Why are you doing it with your credit card points? | Fortune

Amex Membership Rewards points can be used on Amazon, but redeeming them for a vacuum can destroy value compared with transferring points to the right airline partner. Transferring can cover a round-trip flight, while buying an appliance can value each point at less than a cent. Mistakes often happen when points are collected in one place without understanding their worth or best uses. Diversification across cards and loyalty currencies reduces risk. If all spend is directed to one program and that program devalues awards, raises redemption prices, or removes routes, purchasing power can drop with no backup. Holding miles across multiple airlines and issuers provides flexibility and protection from changes.

"“I was like, you can't do that,” Ewen told Fortune. Not because Amex points can't be used on Amazon (they can) but because using them that way destroys their value. Transferred to the right airline partner, those same points could have covered a round-trip flight. Instead, they bought an appliance at a redemption rate that valued each point at less than a cent."

"Ewen has spent two decades in the points and miles space, and one of the principles he returns to most often is diversification. Not just of cards, but of the currencies they earn. “It's just like an investor strategy,” he says. “You don't want to be all in on one stock, because if that stock tanks, you're going to be left out in the cold.”"

"The same logic applies to loyalty programs. If you've put every dollar of spend toward Delta SkyMiles and then Delta devalues its award chart, raises redemption prices, or eliminates a route you rely on, you're stuck. You have a pile of currency that just lost purchasing power and have no backup. “If you are fully in on Delta SkyMiles and then Delta changes something that you don't like, that doesn't give you a ton of flexibility,” Ewen says."

"“Whereas, if you have some miles with Delta, some with United, some with Chase, that allows you to be protected from some of those changes.” The points comparison to portfolio management isn't just a metaphor. Airline loyalty programs are now valued in the tens of billions of dollars-in some cases worth more than the airline"

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