It's not so much how long it lasts (though I had Xtol die in a very few months back when I tried it - this was from the old small packs though so maybe the 5L ones won't do that) but the fact that when it does go, it does so without any visible change in color and, all too often, very suddenly. Works fine one day, the next week you get virtually undeveloped negatives from developer that looks just like it did the previous week when it worked fine.