in 30 years I have only broken one inertia puller, it was the old design with aluminum handle shaft, broke the shaft so drilled out the part in the head and pressed it back together and it lasted 10 years, I called RCBS and they wanted the old one back and would replace it, I had discussion re shipping a broken one back was more than it was worth, a week later I sawn the old one up so it would fit in a envelope and mailed it to them.
month later got a replacement for free, 2 weeks later got a second one, I did call and ask if they wanted the second one back but they said keep it or give it to someone who could use it.
its all in the way its used, if you swing like a hammer hitting a nail you flex the handle, instead swing but relax when it contacts the surface, no flex and easy on the arm if doing a hundred or so, they are good for round nose that can not be gripped by a collet