318 Magnum Dropped Valve

I was surprised that a machine shop asked me if I wanted them to check the valve guide clearances, that should be a given on any valve job. Also I've learned not to reuse the valve's as I had a valve break right below the guide boss, needless to say it not only broke the top of the piston but broke through the cylinder wall. The valve guide issue and the broken valve were both on the same engine a 302 ford