I've read several claims that XTOL has a proclivity to work well for most of the life of a stock solution and then just die. I've been using XTOL with Tri-X, FP4+, Delta 100, and APX 400 for several years now. So far, I have not observed this behavior. I keep my XTOL in a collapsible bottle to minimize air contact and run through a couple gallons in about 3 months. Toward the end, my collapsable bottle cannnot eliminate all air as there is a limit to how much the bottle will collapse. At that stage (at least the last couple of batches I've made) my standard development times for Tri-X are not sufficient to give expected contrast. I will scan the film using my minolta scanner to make the equivalent of a contact sheet. The scanner produces muddy blotchy mid tones when the film is developed using this old developer. At this point I toss the developer and make a fresh batch. I suppose if I ignored the changed behavior and used it to the bitter end, I might see the 'sudden death' syndrome. Although to my mind, it is anything but sudden. I dilute my working solution to 1:1 and typically develop at 68 degrees using the times recommended by the Kodak XTOL datasheet. Has anyone else seen this contrast fall-off before their XTOL dies?