A catalytic converter should NEVER go bad unless something causes it such as a RICH or a LEAN condition.
What is a "RICH OR A LEAN CONDITION"?
As long as the vehicle is kept in good running order the catalytic converter should last the life of the vehicle.
its long gone now, lets put it that way.
8 years or 80,000 miles.
It depends on what kind of converter you purchased. If you purchased a cheap aftermarket converter, then I'd guess it wouldn't last as long as an O.E. Volkswagen one. I'm guessing that your original one lasted seven years, so I'd think that a new one should last that long. It's possible that another problem such as a bad fuel injector or a miss in the engine could cause the engine to dump raw fuel into the converter. This would considerably shorten the life of the converter. A vacuum leak could cause the same problem. It should last more that a year and a half, either way, although it's doubtful that the part will be warranted longer than that.
2 years
It can last the life of the vehicle. But it can be destroyed by an engine not running properly in a very short period of time.
Assuming the engine is tuned correctly and there is a minimal amount of unburned fuel reaching the converter, it should last as long as the car itself. They break down quickly however when a vehicle has a series of misfires causing unburned fuel to reach the converter. If this happens the check engine or MIL light will flash when the converter is being ruined.
Immediately.
As long as the muffler and catalytic converter are intact
not really, as long as it is at the right temperature, it will not be affected
Yes, as long as you install a new one. It is illegal to remove the converter from any vehicle.
Don't let your car idle for long periods of time.