Our tanks don't break, and neither do our competitors which is why a good warranty is very important. You need to know that should the tank break either your insurance would cover it as they would if someone drives into it for instance. Or if there is no apparent reason for the damage, the tank company will cover it.
Our warranties are NOT Pro Rata. Before you accept a Pro Rata warranty, make sure you are getting the tank really cheap. It could cost you a fee to replace the tank under warranty and the fee may be as much as buying a new tank at a readily available special such as a field days price.