I'm going to CDG in March. Cheapest available is ~$1400 in multiple low classes. B is available for ~$2500. Works out to roughly 13cpm for cheap, 15cpm for B. I'd like to upgrade using miles/miles&money at least on the return. Going the former route will cost me $550 + 25k miles to upgrade each way and I'll "only" get 100% pqm. Going the latter route will cost me 20k miles and I'll get 150% pqm. No availability for upgrade on the outbound, but availability on the return. I have $400 in ecerts too, but don't have to use them now as I'll be taking more longer trips throughout the year. If I use my ecerts the B is 12.5cpm. Based on that, any reason I should not get the B fare other than the $900 difference? And assuming you think I should B fare, is it merely a personal choice to use the ecerts now vs later on a flight that is higher cpm? Thanks and I know I should know this answer from my research, travel, reading, but I simply don't.