Not too long, but I trust my work and I'm the guy who doubts everything. It's hard to mess up a head with the set-up I use. I regualrly check the swage with a guage. I also use a Nicopress 510 bench mount with 64-CGMP jaws, none of that crappy campell or other knock off stuff.
I can do copper in 1,2,3 and aluminum in 2,3,4.