A lot less time than it takes to get it off the car. Just take a wooden dowel or something similar and push it or pound it through the cat. Or a large drill bit or anything else to remove the converter honeycomb inside. You don't have to get it all, just a decent sized opening about the same size as the connector pipes.

2001 Sportage, TJ 106's, Everet spacers and bumpstops, Bilstein shocks on the rear, cone filter, Crager wheels, 235-75-15 Goodyear tires. Custom front winch bumper by Dave Scott. Currently DOA, but it is a work in progress.
2011 Kia Forte EX