If people are picking 2 or 2.5 hours because "James can't handle it"... then why not make it a 3 hour set and make the other 30+ minutes instrumentals/jamming, a la extended solos/intros/outros, solo spots, etc. etc.
I refer to Live At Budokan for a GREAT amount of instrumental time that gives James a lot of time to rest between songs - "Beyond This Life" 10 minute jam, the extended intro/solo of "Hollow Years", The Instrumedley, and "Stream Of Consciousness"... all in all, that's a good 35 minutes of instrumental time w/o James on stage.
And even then, if you have solo spots (like just JR, or just JP, or just MP), that gives everyone else in the band a good 5-10 minute break, so it's not like all four instrumentalists are playing the entire night/every song.
-Marc.