Now that Bob's dragged me here, I'll tell my Kilkenny story. I bought two pairs and did a fair amount of running in one pair. I gave the toher to my son to use for indoor track races.
I did just fine in the Kilkenny for quite a while, as Bob mentioned and had run for as long as two hours fifteen in them. Then one day I did feel a bit of an ache in the ball of my left heel after running in them, maybe for 90 minutes (not sure.) I ran in soemthing else the next day and came back to the Kilkenny again and the ache was still there, though it wasn't bad at all.
At this time, my son lost his pair of Kilkennys (Kilkennies?) and had an indoor race in a day or two. As we have the same shoe size, I gave him my pair and haven't run in them since. I have, on occasion, noted the same ache in my left heel, but it's neither bad nor persistent (knock wood.)
I have found that shoes with medial posts give me PFlike problems. I can't say the Kilkenny did or didn't. Well, actually, they didn't, but maybe they would have if I'd kept using them, or maybe not.
As to durability, the thing about a pair of flats is that they'll last until they fall apart. you aren't counting on the shoe for support or cushioning, so there's nothing to wear out. If you can run in the Kilkenny, you probably won't need a new pair for more than a year.