Delta is also one that routinely puts out sales especially in D1. On the flip side they consistently have stealth devaluations so it can be a wash.

The name of the game these days is earn and burn - would only hold onto miles if you have a specific award you are working towards.

Also why many folks in points and miles world have been moving to CC based currencies (Chase UR, AMEX MR, Citi TYP, SPG) for their primary accumulation / spend since those are more immune to devaluations.