I have a large and a small Paterson plastic, which I've had for over thirty years, and a large Durst plastic, which I've had for about a decade. The Patersons are for dev, the Durst for fix. The Patersons have now a network of fine lines mostly parallel to the length, which look like stress marks of some kind, and the plastic has now discoloured a little to a kind of dull greyishness. I'm not sure what causes it ; I don't do anything out of the ordinary like mixing hot solutions in them. My first Paterson cylinder did the same after a couple of years and I replaced it thinking breakage was imminent, but the replacement did the same ; yet the last three decades of regular use have been uneventful, the solutions mix fine, and there's never anything irregular in developments. I used glass measures for years during my laboratory days, and don't recall ever breaking one, but they're toughened low-expansion glass. I'd prefer glass if I could overcome the inertia of laziness to go and find some, but the plastic ones do the business, and I guess good enough is good enough.