What it says on the tin! I no longer get an alert when I use my watering can down to 0 lifespan - no breaking sound, no message. I just find out it's broken when I try to use it again and get the "you need a watering can for that" message.
I have the "Heavy Flow" upgrade to reduce wear and tear on it; I got the upgrade shortly after it became available so I'm not sure whether it has an effect on this happening.