When I first started traveling on business 20 years ago, and signing up for all of the loyalty programs of the airlines I was flying, people used to talk about saving their miles up over a lifetime.

It was common to think of miles as a retirement fund. Some people would travel for work and tell an annual vacation with their family on points. But others just wouldn’t have the time, such is the way Americans think of work and leisure. So they’d accumulate miles over many years with a plan to use those miles ‘some day’. And some day was often thought of as retirement, when there’d be nothing but time.

Devaluations changed all of that. It’s clear that the miles you earn now will never be worth more in the future than they are worth today. In fact pretty much any stash that you sit on for more than a couple of years will become worth less.

While there are no doubt still people who earn miles and do not spend them, the conventional wisdom has shifted completely: earn and burn more or less in the same period, and then earn some more. Saving miles is a fool’s game.

That’s a lesson consumers have learned over and over and very much the hard way. Programs work to convince members their points have value, but then reduce the value of those points. That’s true pretty much across the board, whether activity or spend-based, whether airline or hotel or rental car program.

Bank programs — other than Citi ThankYou Rewards — have often tinkered with future points earning, and less with redemptions, although they certainly change and lose mileage transfer partners. That’s one reason I like focusing my earning with bank programs. Another is flexibility. I try to diversity my earnings across bank programs, too, as a further hedge.

When members earned without redeeming miles, redemption costs to programs were limited and they were pushed out into the future (making those costs lower on a net present value basis).

When members earned without redeeming miles, redemptions were easier because there was less competition for award seats. (There were also fewer members, fewer members with enough miles, and planes weren’t as full — so the speed at which members want to redeem their miles is hardly the only factor here.)

Now that there are more members with more miles who do not trust programs to preserve the value of their points they want to redeem points as soon as possible.

That increases competition for seats And increases redemption costs to programs Putting pressure on the ability of the program to deliver promised benefits (manage redemption relative to capacity) And driving up costs

Which of course provides the impetus for programs to devalue further, to manage their costs and to manage the requests for miles compared to available seats.

Devaluations, ironically, create the need for future devaluations. Although it shouldn’t be surprising as it’s consistent with a currency model of inflation: devaluations change altered consumer expectations so the speed at which miles are redeemed (velocity) grows.

Usually devaluations don’t follow on devaluations right away (except at Delta). But they do follow. We’re usually safe for a couple of years after a big devaluation, but don’t ever expect devaluations to be a one-time event.