What do you determine as a long fight?
HM Ifrit takes ~10 minutes and I thought it was rather sizeable compared to some of the bosses that are downed in 3-4 minutes each.

I personally would enjoy more 'intense' fights than longer ones per se. First time I did Titan without any prior knowledge I was blown away, especially in the final phase where everything is going off. Arguably, the Titan fight probably went for ~7-8 minutes as well. A longer boss fight with intense phases? Sure, why not!