Champ and Z definately hold their flight the longest that I've had. Those who say any of Trilogy's plastic are obvioisly fanboys as every single Opto, Lucid, or VIP disc I've had has beaten in quicker than I would have liked, VIP less so than the others but still too quick for my liking. I typically would play 3-4 times a week on heavily wooded courses so there was a lot of tree hits even at low power. I've also noticed that the change is more sudden than either Champ or Z but VIP doesn't scuff as easily.
I don't know that I'd consider the trilogy plastics the "most durable" as they do beat in relatively quickly, but they do hold that sweet spot for a long time. Fluid plastic has been very durable for me as my fluid escape is pretty much my favorite disc in my bag that I have thrown for 3-4 years now with very little change in flight at all. Champ definitely isn't most durable either as I've had Roc3's go from overstable to dead straight or even getting a bit of turn in a fairly short amount of time.
The one Z disc I have though flies identical to the day I bought it and probably could pass for new if i put a price tag on it and stuck it on a shelf. Granted it hasn't seen a lot of use in the last couple years but used to be my primary forehand disc.