I use old five gallon bottled-water carboys (Arrowhead/Puritas) for fermenters. That's crowding things a little for five-gallon batches, and I've considered buying some modern six or six-and-a-half gallon carboys so I can maybe retire my blow-off tubes. But reading all the horror stories about carboys getting broken or just self-destructing has pretty much scared me out of the idea.
The three I use are all fifty or sixty years old, and much heavier-duty than what I see at my LHBS. They were designed to be manhandled: they were schlepped around in trucks after being cleaned and refilled, carried in and out of houses and offices, and mistreated by folks switching them out on their water coolers. I figure if they've lasted this long, they aren't going to be popping on me unexpectedly....
On the other hand, I treat them with a lot more respect and care than I did before reading what can happen.
