When I've done shredding for office files, I've always hired it done. Here in Colorado, we retain client files for 10 years unless it's been returned to the client.
A couple of people from the shredding company show up outside my filing room driving a 2 1/2 ton truck with an industrial sized shredder that occupies the back. They carry banker's boxes full of files from my file room to the truck and dump them into the shredder. The shredder is done with the box of files before the next guy leaves the file room with the next box.
The last time I shredded files, the file room was a 10 x 10 x 8 room filled with banker's boxes full of files to be shredded. Took them less than 3 hours to finish the job and all fr $350.00
I have no idea what they use to lube their shredder.