Originally Posted by
canadiancow
It's definitely different for everyone, but when Comfort became refundable, I no longer saw any reason to book Flex. No co-pays, fewer eUps, and more AQM are just bonuses.
Recently I paid a ~$70 fare difference (no change fee on Comfort fare) because when my eUp window opened, my flight was R0 but a later one had R space. For $70, it was worth it. If there had been a significant change fee ($200? I don't know what domestic fees are), the math would have been very different. So within your window, you can do the co-pay math (though it's also possible low Flex to G might cost less - not the case with L, but maybe from S), and outside your window, you know you can change your flight for free if there's no R space.
Absolutely, Comfort is a no-brainer choice for me currently. Not touching anything that isn't refundable anyway. You do have an advantage over me though, with my much shorter upgrade window at officially 8 days that fare differences are more likely to be a factor for me if I then make changes but your point still stands that I can maneuver to a flight where I have a chance of an upgrade instead of a lost cause outside that time.