Those of us who by geography or choice are members of OnePass and use our miles for coach tickets have seen an effective devaluation of 50% due to the almost non-existent availability of standard reward tickets, forcing us to use the so-called
EasyPass ("SleasyPass" on the FlyerTalk CO board) awards.

Time will tell if this becomes an industry-wide trend.

Yet this example shows that airline miles are not a good long-term "investment" or "currency." The risks are too great, not only airline de facto devaluation, but also the fact that each and every one of us will die some day, rendering our account balances worthless.

I'm all for earning as many miles as possible, including by FT subscriptions if necessary to achieve my travel goals, but a prudent flyer will spend most of his miles fairly promptly, to avoid the twin risks of death and airline "taxes" (rule-changing award availability devaluation).

To consider miles as a "currency" or an "investment" for retirement is putting wild-eyed optimism over the plain language of the frequent flyer terms and conditions promulgated by each airline. Ignore those terms and conditions at your peril.

So long as those terms and conditions include termination on death, and remain subject to unilateral change by the airline, holding miles for the long term is like consistently betting against a casino.

Miles are best enjoyed now, while they still have (some) value.