I think with any scheme involving the exploitation of market inefficiencies will slowly decline in profitability over time.

We've seen the decline in the FF mile and program opportunities over time. Mileage running used yield tremendous benefits and now rarely does and almost never at the same profit level.

The golden era of manufactured spend is probably past us and newer opportunities are less profitable, with more restrictions, and have a shorter lifespan.

We saw the same thing with the 0% credit card money back in 2006-2008 that could be used for a year earning 5% in savings accounts.